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MAIN  LIBRARY-AGRICULTURE  DEPT. 


- 


CONTENTS 


Page. 

Introductory I 

Historical .> 

( )riginal  description  of  genus 4 

Translation 4 

Synonymy 

Revisional  notes 

•  1  description  of  genus 5 

Anatomical 5 

Nomenclature 

Illustrations...  Q 

•--••-------"------.......  r7 

External  characters  of  the  imago 9 

The  head 11 

The  thorax 22 

Divisions  of  the  thoracic  segment 23 

Elements  of  the  adult  thorax 26 

The  prothorax 26 

The  mesothorax 28 

Mesotergum 28 

Mesoplura fc . .  29 

Mesosterna 30 

The  metathorax 30 

Metatergum 30 

Metapleura 34 

Metasterna 35 

The  abdomen 35 

Abdominal  tergites 36 

Abdominal  pleurites 33 

Abdominal  sternites 33 

Spiracles 39 

The  legs 39 

The  wings ^ 

Mcsothoracic  and  metathoracic  wings 42 

Metathoracic  or  hind  wings .j;j 

Mesothoraric  wings  or  elytra 49 

I nt ernal  anatomy 5^ 

1  »i,urosf  ive  system 52 

•Hilary  sexual  characters -)L> 

PuPa '.^         53 

Larva 5^ 

External  characters 57 

Digestive  system 64 

.......'.'..'.'.        64 

Shyriological  characteristics 


554065 


IS. 


X  ........  ....THE   gCpLS»TlD    BEETLES. 


Pago. 

Specific  distinctions 66 

Range  or  limits  of  specific  variation 66 

Progressive  modifications 67. 

Distinction  of  major  and  minor  divisions  of  the  genus 68 

Plan  of  synoptic  treatment 69 

Synopses  of  morphological  and  physiological  characters 69 

Synopsis  of  adult  characters 69 

Synopsis  of  secondary  sexual  characters 73 

Synopsis  of  pupal  characters 

Synopsis  of  larval  characters 75 

Synopsis  of  gallery  characters 76 

Table  of  distribution 77 

Table  showing  relation  of  species  to  host  trees 

Table  of  host  trees 79 

Revision  and  systematic  notes,  with  descriptions  of  new  species ^     79 

Distinctive  generic  characters 79 

Bibliography  and  synonymy  of  genus 80 

Division  1 81 

Subdivision  A 81 

1.  Dendroclonus  brevicomis  Le  Conte . 81 

2.  Dendroctonus  barberi  n.  sp 85 

3.  Dendroctonus  convexifrons  n.  sp 87 

4.  Dendroctonus  frontalis  Zimmerman 90 

5.  Dendroctonus  arizoni^us  n.  sp .v 95 

6.  Dendroctonus  mexicanus  Hopkins 97 

7.  Dendroctonus  par allelocollis  Chapuis 99 

8.  Dendroctonus  approximatus  Dietz 101 

Subdivision  B 105 

9.  Dendroctonus  monticolx  Hopkins 105 

10.  Dendroctonus  ponderosas  Hopkins 109 

11.  Dendroctonus  jeffreyi  n.  sp 114 

Division  II 116 

Subdivision  C 117 

12.  Dendroctonus  simplex  Le  Conte 117 

13.  Dendroctonus  pseudotsugse,  Hopkins 121 

14.  Dendroctonus  piceapefda  Hopkins 126 

15.  Dendroctonus  engelmanni  n.  sp 130 

16.  Dendroctonus  borealis  n.  sp 133 

17.  Dendroctonus  obesus  (Mannerheim) 135 

18.  Dendroctonus  rufipennis  (Kirby) 138 

19.  Dendroctonus  murrayanse  n.  sp 140 

20.  Dendroctonus  punctatus  Le  Conte 142 

21.  Dendroctonus  micans  (Kugelann) 143 

Subdivision  D 146 

22.  Dendroctonus  terebrans  (Olivier) 147 

23.  Dendroctonus  valens  Le  Conte 151 

24.  Dendroctonus  adjunctus  Blandford 157 

Bibliography 159 


ILLUSTRATIONS 


PLATES. 

Page. 

PLATE  I.  Classification  of  the  genus  Dendroctonus,  showing  technical  and  com- 
mon names  and  species  numbers 1 

II.  Map  of  world,  showing  geographical  distribution  of  the  genus  Den- 
droctonus    80 

III.  Dendroctonus  adults.     Fig.   1. — D.  brevicomis.     Fig.  2. — D.  barberi. 

Fig.  3. — D.  convexifrons.     Fig.  4. — D.  frontalis.     Fig.  5. — D.  ari- 

zonicus.     Fig.  6. — D.  mexicanus.     Fig.  7. — D.  parallelocollis 164 

IV.  Dendroctonus  adults.     Fig.  8. — D.  approximates.     Fig.  9. — D.  monti- 

colse.     Fig.  10. — D.  ponderosx.     Fig.  11. — D.  je/reyi 164 

V.  Dendroctonus  adults.     Fig.  12.— D.  simplex.     Fig.   13.— D.  pseudo- 

tsugse.     Fig.  14. — D.  piceaperda.     Fig.  16. — D.  borealis 164 

VI.  Dendroctonus  adults.     Fig.  17. — D.  obesus.     Fig.  18. — D.  rufipennis. 

Fig.  20. — D.  punctatus.     Fig.  21. — D.  micans 164 

VII.  Dendroctonus  adults.     Fig.  22.— D.  terebrans.     Fig.  23.— D.  miens 164 

VIII.  Dendroctonus  larvae.     Fig.  1. — D.  brevicomis.     Fig.  19. — D.murrayanae. 

Fig.  23.— D.  valens 164 

TEXT   FIGURES. 

FIG.    1.  Dendroctonus  valens:  Adult,  dorsal  aspect 6 

2.  Dendroctonus  valens:  Adult,  ventral  aspect 8 

3.  Dendroctonus  valens:  Adult,  lateral  aspect 9 

4.  Dendroctonus  valens:  Head,  dorsal  and  lateral  aspects 12 

5.  Dendroctonus  valens:  Head,  ventral  aspect,  and  mouthparts 13 

6.  Dendroctonus  valens:  Head,  oral  aspect,  epistoma,  etc 14 

7.  Pterostichus  californicus:  Head,  dorsal  and  ventral  aspects 15 

8.  Pissodes  strobi:  Head,  ventral  aspect,  and  mouthparts 16 

9.  Pissodes  strobi:  Head,  dorsal  aspect,  and  mandibles 17 

10.  Dendroctonus:  Epistomata 19 

11.  Dendroctonus:  Antennae 20 

12.  Dendroctonus:  Antennae 20 

13.  Dendroctonus:  Antennae 21 

14.  Dendroctonus  valens:  Mandible 22 

1  •">.   Dendroctonus:  Eyes 23 

16.  Dendroctonus  valens:  Areas  of  pronotum 23 

17.  Dendroctonus  valens:  Areas  of  prothorax,  ventral  aspect 24 

18.  Dendroctonus  valens:  Mesothorax,  ventral  aspect 24 

19.  Dendroctonus  valens:  Mesotergum  and  mesopleurum 28 

20.  Dendroctonus  valens:  Metatergum  and  metapleurum 31 

21.  Dendroctonus  valens:  Metatergum,  inner  aspect 33 

22.  Dendioctonus  valens:  Abdominal  tergites 35 

23.  Dendioctonus  valens:  Male,  abdominal  tergites  7  and  8 36 

24.  Dendroctonus  valens:  Female,  abdominal  tergites  7  and  8 37 

XI 


xii          ,*  ;:•;»*:   -."ME  ^SC^EYTID  BEETLES. 
,'• ,»'  :;;  .•*;",»'  ':  i ..:  •'•'••.•' 

Page. 

FIG.  25.  Dendroctonus  valens:  Abdominal    sternites,    ventral    and    lateral    as- 
pects   38 

26.  Dendroctonus  nolens:  Tibia,  tarsus,  articulation,  etc 40 

27.  Dendroctonus:  Left  tibiae,  dorsal  and  ventral  aspects 41 

28.  Dendroctonus:  Left  tibiae,  dorsal  and  ventral  aspects 42 

29.  Dendroctonus:  Left  tibiae,  dorsal  and  ventral  aspects 43 

30.  Dendroctonus  valens:  Diagram  of  basal  area  of  hind  wing 44 

31.  Dendroctonus  valens:  Right  elytron,  ventral  aspect 45 

32.  Dendroctonus  valens:  Basal  process  of  right  elytron 46 

33.  Dendroctonus  valens:  Decli vital  section  of  elytra 46 

34.  Dendroctonus  valens:  Diagram  of  elytron,  showing  striae,  interspaces, 

and  tracheae 47 

35.  Dendroctonus  valens:  Digestive  organs  of  adult t 52 

36.  Dendroctonus  valens:  Fore  intestine,  showing  details 53 

37.  Dendroctonus  valens:  Pupa,  dorsal,  lateral,  and  ventral  aspects 54 

38.  Dendroctonus  valens:  Pupa,  lateral  and  anal  aspects 55 

39.  Dendroctonus  valens:  Larva,  dorsal,  lateral,  and  ventral  aspects 58 

40.  Dendroctonus  valens:  Head  of  larva 59 

41.  Dendroctonus  valens:  Mouthparts  of  larva 60 

42.  Dendroctonus  valens:  Mandibles  of  larva 63 

43.  Dendroctonus  valens:  Digestive  organs  of  larva 65 

44.  Dendroctonus  brevicomis:  Egg  galleries 82 

45.  Dendroctonus  brevicomis:  Bark  showing  pupal  cells,  exit  burrows,  and 

pitch  tubes 83 

46.  Dendroctonus  brevicomis:  Distribution  map 84 

47.  Dendroctonus  barberi:  Egg  galleries 86 

48.  Dendroctonus  barberi:  Distribution  map 87 

49.  Dendroctonus  convexi/rons:  Egg  galleries  and  larval  mines 89 

50.  Dendroctonus  convexifrons:  Distribution  map 90" 

51.  Dendroctonus  frontalis:  Egg  galleries  and  larval  mines 91 

52.  Dendroctonus  frontalis:  Termination  of  egg  galleries 92 

53.  Dendroctonus  frontalis:  Beginning  of  egg  galleries 92 

54.  Dendroctonus  frontalis:  Bark  showing  pitch  tubes,  etc 92 

55.  Dendroctonus  frontalis:  Old  egg  galleries  in  living  tree 93 

56.  Dendroctonus  frontalis:  Egg  gallery  in  living  tree,  the  resulting  wound 

in  process  of  healing 93 

57.  Dendroctonus  frontalis:  Distribution  map 94 

58.  Dendroctonus  arizonicus:  Distribution  map 97 

59.  Dendroctonus  mexicanus:  Section  of  egg  galleries 98 

60.  Dendroctonus  mexicanus:  Distribution  map 99 

61.  Dendroctonus  parallelocollis:  Section  of  egg  gallery 100 

62.  Dendroctonus  parallelocollis    Distribution  map 101 

63.  Dendroctonus  approximatus:  Single  egg  gallery 102 

64.  Dendroctonus  approximatus:  Egg  galleries 103 

65.  Dendroctonus  approximatus:  Distribution  map 104 

66.  Dendroctonus  monticolse:  Egg  galleries  and  larval  mines  in  bark 107 

67.  Dendroctonus  monticolx:  Egg  galleries  and  larval  mines  grooved  in  sur- 

face of  wood 108 

68.  Dendroctonus  monticolse:  Distribution  map. . .  .*. 109 

69.  Dendroctonus  ponderosse:  Egg  galleries  and  larval  mines 112 

70.  Dendroctonus  ponderosx:  Tree  with  bark  removed,  showing  egg  gal- 

leries grooved  and  marked  on  surface  of  wood 113 

71.  Dendroctonus  ponderosx:  Distribution  map ]  14 


ILLUSTRATIONS.  XIII 

Page. 

FK  ; .  72.  Dendroctonus  jeffreyi:  Distribution  map 116 

73.  Dendroctonus  simplex:  Egg  galleries  and  larval  mines 119 

74.  Dendroctonus  simplex:  Distribution  map 120 

75.  Dendroctonus  pseudotsugse:  Egg^galleries  and  larval  mines 122 

76.  Dendroctonus  pseudotsugse:  Egg  gallery  and  larval  mines 123 

77.  Dendroctonus  pseudotsugse:  Section  of  log  with  bark  removed,  showing 

brood  galleries  marked  and'  grooved  on  surface  of  wood 124 

78.  Dendroctonus  pseudotsugx:  Distribution  map 125 

79.  Dendroctonus  piceaperda:  Egg  gallery  and  larval  mines 128 

80.  Dendroctonus  piceaperda:  Distribution  map 129 

81.  Dendroctonus  engelmanni:  Egg  gallery  and  eggs  in  living  bark 132 

82.  Dendroctonus  engelmanni:  Distribution  map 133 

83.  Dendroctonus  borealis:  Distribution  map 134 

84.  Dendroctonus  obesus:  Distribution  map 137 

85.  Dendroctonus  rufipennis:  Distribution  map 140 

86.  Dendroctonus  murrayanse:  Distribution  map 141 

87.  Dendroctonus  punctatus:  Distribution  map 143 

88.  Dendroctonus  micans:  Egg  galleries  and  larval  chamber 145 

89.  Dendroctonus  micans:  Distribution  map 146 

90.  Dendroctonus  terebrans:  Distribution  map 150 

91.  Dendroctonus  valens:  Egg  galleries  and  larval  chamber 152 

92.  Dendroctonus  valens:  Work  in  bark  at  base  of  stump 153 

93.  Dendroctonus  valens:  Basal  wound  in  living  tree  resulting  from  primary 

injury  by  this  species 154 

94.  Dendroctonus  valens:  Distribution  map 155 

95.  Dendroctonus  adjunctus:  Distribution  map 158 


Tech.  Series  17,  Part  I,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


PLATE  I. 


11 


02  H 

1.  brevicomis  Lee.  1. 

2.  6ar6m  Hopk.  2. 

3.  convexifrons  Hopk.  3. 

4.  frontalis  Zlmm.  4. 

5.  arizonicus  Hopk.  5. 

6.  mexicanus  Hopk.  6. 

7.  parallelocollis  Chap.  7. 

8.  approximatus  Dietz.  8. 


Western      Pine    70,81 

Beetle. 
Southwestern  Pine  70, 85 

Beetle. 
Roundheaded  Pine  70, 87 

Beetle. 

Southern     Pine    70,90 

Beetle. 
Arizona  Pine  70,95 

Beetle. 

Smaller     Mexican    70, 97 

Pine  Beetle. 
Larger  Mexican  70,99 

Pine  Beetle. 
Colorado  Pine  70,101 

Beetle. 


9.  monticolse  Hopk.        9. 

10.  ponderosse  Hopk.      10. 

11.  jeffreyi  Hopk.  11.  Jeffrey  Pine  Beetle  71, 114 


Mountain     Pine  71, 105 

Beetle. 
Black  Hills  Beetle  71, 109 


Position  doubtful — 


12.  simplex  Lee.  12.  Eastern    Larch  71, 117 

Beetle. 

13.  pseudotsugte  Hopk.  13.  Douglas  Fir  Beetle  71, 121 

14.  piceaperdct  Hopk.     14.  Eastern  Spruce  71,126 

Beetle. 

15.  engelmanni  Hopk.    15.  Engelmann  Spruce  71, 130 

Beetle. 

16.  ftoreaftsHopk.          16.  Alaska      Spruce  72,133 

Beetle. 

17.  obesus  Mann.  17.  Sitka  Spruce  Beetle  72,135 


18.  rufipenni*  Kirby.      18.  Redwinged     Pine  72,138 

Beetle. 

19.  murrayante  Hopk.    19.  Lodgepole    Pine  72,140 

U  Beetle. 

20.  Allegheny    Spruce  72, 142 
Beetle. 

21.  micans  Kug.  21.  European     Spruce  72, 143 

Beetle. 

22.  terebrans  Oliv.          22.  Black    Turpentine  72,147 

Beetle. 

23.  valens  Lee.  23.  Red     Turpentine  72, 151 

Beetle. 

24.  adjunctus  Blandf.     24.  Guatemala    Beetle        157 


Classification  of  the  Genus  Dendroctonus,  Showing*  Technical  and  Common 
Names  and  Species  Numbers. 

This  diagram  will  enable  the  reader  to  refer  at  once  to  the  technical  and  common  names 
of  any  species  number  mentioned  in  the  text,  and  will  show  at  a  glance  the  position 
and  relations  of  the  divisions,  subdivisions,  sections,  subsections,  series,  and  species 
into  which  the  genus  is  divided. 


T.  S.  D.  A..  B.  K.  Tech.  Scr.  17.  I't.  I.  F.  I.  I.,  June  30,1909. 

CONTRIBUTIONS  TOWARD  A  MONOGRAPH  OF  THE 
SCOLYTID  BEETLES. 


I.  THE  GENUS  DENDROCTONUS. 

By  A.  D.  HOPKINS. 
In  Charge  of  Forest  Insect  Investigations. 

INTRODUCTORY. 

The  active  work  on  forestfinsects  conducted  by  the  West  Virginia 
Agricultural  Experiment  Station  in  1890-9£i,  and  by  the  Division  and 
Bureau  of  Entomology  of  the  U.  S.  Department  of  Agriculture  since 
1899,  has  resulted  in  the  accumulation  of  a  mass  of  systematic  and 
biological  data  on  the  principal  described  and  undescribed  insect  ene- 
mies of  forest  trees  and  forest  products  of  the  United  States.  When- 
ever an  attempt  has  been  made,  however,  to  work  up  the  material 
relating  to  a  given  species,  or  group  of  species,  it  has  been  apparent 
that  the  publication  of  anything  without  first  describing  the  new 
species  and  revising  the  data  in  both  the  systematic  and  economic 
literature  would  contribute  to  confusion  rather  than  to  advancement. 
Indeed,  it  becomes  more  and  more  evident  that  in  order  to  give  reliable 
information  on  applied  entomology  we  must  have  at  our  command  the 
knowledge  gained  by  careful  technical,  or  systematic,  studies  of  the  insects 
with  which  we  have  to  deal.  Therefore,  when  we  find,  as  we  do  in  many 
cases,  that  the  published  results  of  systematic  work  on  a  given  genus 
or  species  are  meager  or  otherwise  unsatisfactory,  it  becomes  necessary 
to  revise  and  verify  the  descriptions  and  biological  records,  and  to 
adjust  the  classification  to  meet  the  requirements  of  the  newly  dis- 
covered facts  relating  to  the  described  and  undescribed  species. 

The  genus  Dendroctonus  presents  a  striking  example  of  the  need  of 
systematic  study  as  a  basis  for  economic  investigation.  It  is  both 
the  most  important  group  of  insect  enemies  of  the  coniferous  forest 
trees  of  North  America  and  one  of  the  most  difficult  for  systematic 
study.  Le  Conte  (1876)  expressed  the  difficulty  met  with  in  a  study 
of  the  species  when  he  said  in  his  later  revision : 

If  I  have  failed  to  indicate  more  strongly  the  differences  between  these  species,  it 
is  because  they  are  not  distinguishable  by  any  prominent  or  definite  characters;  and 
the  student  who  may  have  difficulty  in  identifying  the  species  as  here  defined  would 
have  almost  equal  difficulty  if  the  specimens  in  my  collection  were  before  him. 

1 


THE   SCOLYTID  BEETLES. 


within'  recent  years  little  progress  had  been  made  toward  the 
*aKd  :.cl^£  definition  of  the  specific  and  sexual  characters. 
In*  consequence  the  identification  of  the  species  was  both  difficult  and 
uncertain  and  has  led  to  much  confusion  in  both  systematic  and  eco- 
nomic literature.  With  our  prasent  knowledge  of  the  genus,  based 
on  an  exhaustive  study  of  the  systematic  and  biologic  details,  most, 
if  not  all,  of  the  difficulties  have  been  removed,  so  that  the  identifi- 
cation of  the  species  is  comparatively  easy. 

It  is  the  purpose  of  this  paper  to  revise  and  bring  up  to  date  the 
available  information  on  the  described  species,  to  describe  those  that 
appear  to  be  new  to  science,  and  to  record  the  results  of  original  inves- 
tigations relating  to  the  more  technical  details  that  can  not  well  be 
included  in  the  paper  which  is  to  follow  as  a  part  of  a  bulletin  in  the 
regular  series  and  which  will  give  full  information  on  the  bionomic 
features. 

The  material  which  has  served  as  a  basis  for  the  study  of  this  genus 
consists  mainly  of  the  notes  and  specimens  taken  by  the  writer  in  the 
field  during  his  connection  with  the  West  Virginia  Agricultural 
Experiment  Station,  between  1890  and  July,  1902,  including  special 
investigations  for  the  Division  of  Entomology,  U.  S.  Department  of 
Agriculture,  in  1899,  1900,  and  1901,  and  those  taken  during  the 
investigations  by  this  Bureau  between  July,  1902,  and  July,  1908. 
In  addition  to  the  large  amount  of  material  thus  accumulated  the 
writer  has  studied  the  type  and  other  specimens  in  the  larger  collec- 
tions of  this  country. 

The  writer  desires  to  acknowledge,  in  this  connection,  the  assist- 
ance rendered  by  the  following  gentlemen  in  providing  facilities  for 
the  study  of  specimens  in  the  collections  of  which  they  have  charge  : 
Mr.  Samuel  Henshaw,  in  charge  of  the  Le  Conte  collection  in  the 
Museum  of  Comparative  Zoology,  Cambridge,  Mass.,  and  of  the  Harris 
collection,  Boston  Society  of  Natural  History;  Dr.  Henry  Skinner, 
in  charge  of  the  Horn  collection  of  the  American  Entomological 
Society  and  the  general  collection  of  the  American  Entomological 
Society,  Philadelphia,  Pa.;  Mr.  E.  A.  Schwarz,  honorary  custodian  of 
Coleoptera  in  the  Division  of  Insects,  U.  S.  National  Museum;  Dr. 
W.  G.  Dietz,  who  loaned  type  and  other  specimens  from  his  collec- 
tion, and  Mr.  C.  O.  Waterhouse,  of  the  British  Museum,  who  com- 
pared specimens  with  the  type  of  Dendroctonus  rufipennis  Kirby. 

It  also  gives  the  writer  pleasure  to  acknowledge  the  efficient  assist- 
ance of  Messrs.  J.  L.  Webb,  II.  E.  Burke,  and  W.  F.  Fiske  in  the  field 
and  office  work,  of  Mr.  E.  J.  Kraus  in  the  more  recent  office  work,  and 
of  Messrs.  J.  F.  Strauss  and  R.  E.  Snodgrass  in  the  preparation  of  the 
illustrations  for  this  part  of  the  bulletin. 


THE   GENUS   DENDBOCTONUS.  3 

«  HISTORICAL. 

The  genus  Dendroctonus  was  described  by  Dr.  W.  F.  Erichson  (1836) 
>    include    (Bostrichus]    micans^   Kug.,    (Scolytus}    terebrans    Oliv., 
(Dcnnestes)  piniperda  L.,  (Hylesinus)  minor  Hartig,  and  (Hylesinus} 
minimus  Fab.  " 

Eichhoff  (1864)  revised  the  genus  and  referred  D.  piniperda  (L.)  and 
D.  minor  (Hartig)  to  Blastophagus  Eichh.  and  later  (1879)  to  MyelopJii- 
lus  Eichh.,  and  D.  minimus  (Fab.)  to  Carphoborus  Eichh.,  leaving  D. 
in  leans  (Kug.)  as  the  type. 

Lacordaire  (1868)  referred  to  the  synonymy  and  revised  the  descrip- 
tion, including  Dendroctonus  junipiri  Doeb.  [  =  PJilwosinus  junipfri  &> 
(Doeb.)],  D.  valens  Lee.,  and  D.  similis  Lee.  / 

Zimmerman  (1868)  divided  the  genus  into  three  groups,  placing 
D.  bifurcus  (=  Carphoborus  bifurcus  Eichh.)  in  the  first,  none  in  the 
second,  and  D.  terebrans  (Oliv.)  and  D.  frontalis  Zimm.  in  the  third 
group. 

Le  Conte  (1868)  revised  the  classification  for  the  North  American 
species  to  include  D.  terebrans  (Oliv.),  Hylurgus  obesus Mann.,  Hylurgus 
rujiprnnis  Kirby,  D.  frontalis  Zimm.,  and  two  new  species,  D.  punctatus 
Lee.,  and  D.  simplex  Lee.  He  here  referred  D.  valens  Lee.  to  D.  tere- 
brans (Oliv.),  and  D.  similis  Lee.  to  D.  obesus  (Mann.) .  He  recognized 
t  wo  divisions,  Division  B  represented  by  D.  frontalis,  and  Division  A 
by  the  other  five  species. 

Chapuis  (1869)  included  D.  micans  (Kug.),  D.  valens Lee.,  D.  tere- 
brans (Oliv.),  D.  obesus  (Mann.),  and  added  one  new  species,  D.  paral- 
lelocollis  Chap.,  but  did  not  recognize  D.  frontalis  Zimm. 

Le  Conte  (1876)  included  D.  terebrans  Lac.  (  =  Oliv.),  D.  similis 
Lee.,  D.  rujipennis  (Kirby),  D.  punctatus  Lee.,  D.  simplex  Lee.,  D.  fron- 
talis Zimm.,  and  one  new  species,  D.  brevicomis  Lee.  He  here 
restored  D.  similis  and  omitted  D.  obesus. 

Dietz  (1890)  in  his  "  Notes  on  the  Species  of  Dendroctonus  of 
Boreal  America,"  revised  the  classification,  principally  on  the  char- 
acter of  the  epistoma,  which  he  considered  of  primary  importance 
in  separating  the  species.  He  included  D.  terebrans,  with  varieties 
a,  6,  c-j  d,  D.  rufipennis,  D.  similis  Lee.,  D.  simplex  Lee.,  D.  frontalis, 
added  one  new  species,  D.  approximatus  Dietz,  and  referred  D.  puncti- 
collis  Lee.  to  D.  rufipennis  (Kirby)  and  D.  brevicomis  Lee.  to  D. 
frontalis  Zimm. 

Blandford  (1897)  mentioned  D.  terebrans  (Oliv.),  D.  parallelocollis 
Chap.,  and  an  undescribed  species  from  Texas — probably  D.  terebrans 
(Oliv.) — and  added  one  new  species,  D.  adjunctus  Blandf. 

The  writer  (Hopkins,  1899a)  referred  to  D.  terebrans,  D.  rufipennis 
(Kirby),  D.  simplex  Lee.,  and  D.  frontalis  Zimm.,  with  descriptions  of 

79980—09 2 


4  THE   SCOLYTID   BEETLES. 

different  stages,  habits,  etc.,  of  D.  frontalis,  and  larvae  and  habits  of 
D.  terebrans  (  =  D.  valens).  In  1901  he  described  D.  piceaperda  in 
all  stages  in  connection  with  an  account  of  habits,  seasonal  history, 
etc.,  and  referred  to  the  type  of  D.  rufipennis  (Kirby).  In  1902  he 
described  D.  ponderosse  in  all  stages,  in  connection  with  an  account  of 
habits,  seasonal  history,  etc.  In  1 902,  under  "  Some  Notes  on  the  Genus 
Dendroctonus,"  he  referred  to  a  statistical  method  of  determining 
natural  positions  of  the  species,  and  gave  a  list  of  described  species 
and  manuscript  names  of  undescribed  species,  as  follows:  D.  pinicida 
MSS.,  D.  arizonicus  MSS.,  D.  monticola  MSS.,  D.  ponder  osse  Hopk. 
MSS.,  D.  Jceeni  MSS.,  D.fletcheri  MSS.,  D.  piceaperda  Hopk.,  D.  dietzi 
MSS.,  D.  californicus  MSS.,  D.  shoshone  MSS.,  D.  wickJiami  MSS., 
and  D.  borealis  MSS.  He  restored  D.  brevicomis  Lee.  and  D.  punctatus 
Lee.  from  Dietz's  synonymy,  and  recognized  D.  obesus  (Mann).  In 
1905  he  described  D.  pseudotsugse  and  D.  monticola  in  connection 
with  accounts  of  habits,  seasonal  history,  etc. 

ORIGINAL  DESCRIPTION  OF  GENUS. 

Dr.  W.  F.  Erichson  (1836)  described  the  genus  Dendroctonus  as 

follows : 

DENDROCTONUS. 

[p.  52]  Antennae  funiculo  5-articulato,  capitulo  4-annulato,  suborbiculari,  com- 
presso.  Tibiae  extus  denticulatae. 

Palpi  maxillares  articulo  primo  brevissimo,  secundo  maximo,  sequentibus  duobus 
sensim  minoribus.  Labium  fortiter  compressum.  Palpi  labiales  articulo  primo 
longiore,  subclavato,  secundo  tenuiore,  cylindrico,  minuto,  tertio  obtuse  subulate. 
Antennae  breves,  scapo  clavato,  funiculi  articulo  primo  breviter  clavato,  secundo 
obconico,  reliquis  brevibus  transversis;  capituli  segmentum  primum  reliquis  con- 
junctis  aequale,  politum.  [p.  53]  Corpus  oblongum,  cylindricum.  Rostrum  brevis- 
simum.  Prosternum  antice  obsolete  impressum.  Coxae  anticae  approximatae.  Tibiae 
compressae,  extus  denticulatae.  Tarsi  articulo  tertio  dilato,  bilobo.  Elytra  margine 
antico  elevato. 

[Translation.] 

Antennae  with  5-jointed  funicle;  the  club  suborbiculate,  com- 
pressed, with  four  segments  (annulae).  Tibiae  externally  denticulate. 

Maxillary  palpi  with  the  first  joint  very  short,  the  second  the 
longest,  the  two  following  gradually  smaller.  Labium  strongly  com- 
pressed. The  labial  palpi  with  the  first  joint  rather  long,  subclavate, 
the  second  joint  more  slender,  cylindrical,  small,  the  third  obtusely 
subulate.  Antennas  short,  scape  clavate,  first  joint  of  funicle  shortly 
clavate,  second  joint  obconical,  the  remaining  joints  short,  trans-' 
verse;  first  segment  of  club  equal  to  the  others  conjointly,  polished. 

Body  oblong,  cylindrical.  Beak  very  short.  Prosternum  ante- 
riorly obsoletely  impressed.  Anterior  coxae  approximate.  Tibiae 
compressed,  externally  denticulate.  Tarsi  with  the  third  joint 
dilated  and  bilobed.  Elytra  with  the  anterior  margin  elevated. 


THE   GENUS  DENDROCTONUS.  5 

SYNONYMY. 

The  following  species  were  included,  all  but  two  of  which  were 
subsequently  referred  by  Eichhoff  (1864)  to  other  genera: 

Bostrichus  micans  Kugelann  =  Dendroctonus micans  (Kugelann) . 

(Type -of  genus.) 

Scolytus  terebrans  Olivier  =  Dendroctonus  terebrans  (Olivier). 
Dermestes    piniperda    Linnaeus  =  Myelophilus   piniperda  (Lin- 
naeus). 

II)/lurgus  minor  Hartig  =  Myelophilus  minor  (Hartig). 
Ilylesinus   minimus  Fabricius  =  Carphoborus  minimus  (Fabri- 
cius.) 

BE  VISIONAL   NOTES. 

The  generic  characters  mentioned  by  Erichson  in  the  original 
description  are  recognized  in  the  type  and  other  species  except  that 
the  maxillary  palpi  are  not  4-jointed.  The  first  or  basal  joint  has  a 
basal  ring  or  outward  curved  basal  margin  for  the  attachment  of  the 
membrane  connecting  the  joint  with  the  palpiger.  This  might  have 
been  mistaken  for  the  "very  short  first  joint"  referred  to,  but  it  is 
evident  that  this  or  any  other  structure  does  not  represent  such  a  basal 
joint.  In  the  type  species  the  first  joint  of  the  club  is  equal  to  the 
others,  but  ranges  from  shorter  to  longer  in  the  other  species. 

Le  Conte's  added  characters  in  his  revision  of  1868  and  1876  are 
generally  correct,  except  that  the  antennal  club  is  not  always  concave 
on  one  (external)  side  or  anterior  face,  the  sutures  are  more  often 
curved  than  straight,  and  in  some  species  only  two  sutures  are 
visible  on  one  side  of  the  club.  The  prosternum  is  sometimes  flat,  the 
fifth  joint  of  the  tarsus  is  never  longer  than  the  others  united,  and  the 
ventral  segments  are  only  approximately  equal  in  length,  the  last 
one  being  usually  as  long  as  the  two  preceding  combined. 

Dietz  (1890)  called  attention  to  the  unreliability  of  the  sutures  and 
joints  of  the  antennal  club  in  dried  specimens,  and  laid  special  stress 
on  the  value  of  the  epistoma  in  distinguishing  the  species.  It  appears, 
however,  that  while  the  form  of  the  epistoma  is  a  good  generic  and 
Bubdivisional  character,  it  is  of  little  or  no  value  in  distinguishing  the 
species. 

The  additional  generic  characters  recognized  by  the  writer  will  be 
found  described  under  external  and  internal  anatomy,  and  the  char- 
acters distinguishing  the  major  and  minor  divisions  will  be  found  in  the 
synoptic  tables. 

REVISED  DESCRIPTION  OF  GENUS. 
ANATOMICAL. 

The  following  discussion  of  anatomical  details  includes  the  imago, 
larva,  and  pupa,  and  is  based  primarily  on  the  results  of  original 
dissections  and  anatomical  investigations  by  the  author  during  the 


6 


THE   SCOLYTID   BEETLES. 


past  eighteen  years,  and  of  those  conducted  by  assistants  under  his 
immediate  supervision  during  the  past  three  years. 


OOOOOO  0  6^0 

oooV 

00000000009-6°° 


Dendroctonus  valens  Lee.  has  served  as  the  principal  subject  for 
dissection,   comparison,    and  illustration,    both   on   account   of   the 


THK   GENUS  DENDHOCTONU8.  7 

abundance  of  material  at  hand  and  because  of  the  comparatively 
large  si/e  of  the  individuals  of  this  species.  Sufficient  comparative 
studios  have  been  made,  howeve^,  of  the  other  species  of  the  genus 
and  of  representatives  of  other  genera  of  the  family  and  suborders  to 
form  a  reliable  -basis  for  the  interpretations  and  conclusions  relating 
to  the  more  important  taxonomic  characters  and  the  significance  of 
their  modifications  in  the  distinction  of  species,  genera,  etc. 

Through  the  assistance  of  Mr.  R.  E.  Snodgrass  an  extensive  investi- 
gation has  also  been  made  of  the  thoracic  segments  of  representa- 
tives of  all  of  the  principal  orders  of  insects.  The  results  have 
served  as  additional  data  and  evidence  on  which  to  base  conclusions 
in  this  paper,  and  will  be  utilized  by  Mr.  Snodgrass  as  a  basis  for 
a  more  detailed  discussion  in  a  paper  entitled  "The  Thorax  of  Insects 
and  the  Articulations  of  the  Wings/'  to  be  published  later.  This 
will  include  a  quite  complete  bibliography  and  references  to  the 
principal  systems  of  nomenclature  proposed  or  adopted  by  the  lead- 
ing authors,  thus  rendering  it  unnecessary  to  include  extensive 
bibliographic  references  in  the  present  paper. 

In  all  of  this  anatomical  work  the  object  of  the  author  has  been  to 
acquire  direct  information  on  the  facts  as  they  exist  in  the  subjects  ex- 
amined ;  such  information  to  furnish  a  basis  for  the  determination, 
naming,  description,  and  illustration  of  the  anatomical  elements  as 
represented  in  the  scolytid  beetles,  and  at  the  same  time  to  serve 
as  a  guide  to  the  determination  of  further  facts  relating  to  insect 
anatomy  in  general. 

The  literature  on  insect  anatomy  has  been  utilized  as  a  guide  in 
securing  additional  information  on  the  facts  and  principles  involved, 
and  with  the  idea  of  adopting  such  interpretations  and  nomen- 
clature as  appeared  to  conform  more  nearly  to  the  facts  and  con- 
tribute to  uniformity.  No  attempt  is  made  to  discuss  the  merits 
of  opposing  opinions  or  theories,  or  to  prove  or  disprove  them. 

In  this  presentation  of  the  results  of  independent  investigation 
and  discussion  of  the  facts  as  interpreted  by  the  author,  it  is  hoped 
that  something  has  been  accomplished  toward  the  advancement  of 
information  on  the  general  subject  of  insect  anatomy,  and  that  its 
special  reference  to  the  anatomy  of  the  scolytid  beetles  will  make 
tlu'  future  systematic  study  of  this  troublesome  group  less  difficult 
and  more  accurate,  and  thus  lead  to  the  determination  of  bionomic 
and  economic  data  of  immediate  practical  importance. 

NOMENCLATURE. 

There  is  yet  much  confusion  in  the  literature  and  considerable 
difference  of  opinion  among  the  best  authorities  in  regard  to  ana- 
tomical nomenclature  as  applied  to  the  structure  of  insects  in  gen- 
eral and  especially  to  representatives  of  different  orders.  There  is 


THE   SCOLYTID   BEETLES. 


~^__  —  Epistemw 

_ Exocoxal  piece 

Epimerum 

Stcrndlar  area 
~  'Coxa 
Sternum 
Episternum 
Median  line 
Sternellar  piece 


2. — Dendroctonus  valens:  Adult,  ventral  aspect.    «,  Sternellar  area.    (Original.) 


\S 


THE   GENUS   DENDROCTONUS. 


9 


evidently  much  room  for  improvement  in  the  line  of  uniformity  in 
names  and  interpretations.  In  the  present  paper  the  writer  has 
endeavored  to  adhere  to  the  more  generally  accepted  names  proposed 


HEAD 


Afesosternum 
'.pisi 

E.Tocoxal  area 
Epnncrinn  -  -  - 
Metaslernum 


'-.Pri-scutal  lobe 
-  - :  /-^-  -  -  Clavicle  process 


*--     --^   I 

^"""Coracoid  process 


Trochanter  --/- 
Hind  leg 


FIG.  Z.—Dendroctonus  valens:  Adult,  lateral  aspect,    a,  Pleural  clavicula;  6,  pregena.    (Original.) 


by  Audouin  and  other  writers  for  the  principal  parts,  and  to  suggest 
only  such  revisions  and  new  names  as  the  immediate  requirements  of 
clear  definition  in  comparative  anatomy  and  taxonomy  appear  to 
demand. 


10  THE  SCOLYTID  BEETLES. 

ILLUSTRATIONS . 

The  figures  are  intended  to  be  sufficiently  complete  to  leave  little 
to  be  added  in  the  way  of  description,  except  to  emphasize  and 
elucidate  some  of  the  more  important  features,  or  to  call  attention 
to  the  variation  within  the  genus  or  species. 

EXTERNAL  CHARACTERS  OF  THE  IMAGO. 

The  structural  details  and  general  external  anatomy  and  sculpture 
are  shown  in  figures  1,  2,  and  3.  The  principal  characters  peculiar 
to  the  genus. are  found  in  the  large,  prominent  head,  the  epistomal 
process  (figs.  2,  3,  4,  6,  10)  (referred  to  by  Dietz  as  the  median  seg- 
ment of  the  epistoma),  the  form  of  the  antenna  (figs.  11,  12,  13), 
the  approximate  or  subcontiguous  anterior  coxse  (fig.  2),  and  the 
strongly  recurved  hypopleural  sutures  4,  5,  and  6  of  the  abdominal 
sternites  (fig.  25). 

Length  and  relative  proportions. — The  length  of  the  imago  ranges 
from  2.5  mm.  in  D.  frontalis  to  9  mm.  in  D.  valens.  There  is  con- 
siderable range  in  length  within  the  limits  of  some  of  the  species, 
while  in  others  the  length  is  more  constant.  The  relative  propor- 
tions of  the  width  of  the  head,  width  and  length  of  the  prothorax, 
width  and  length  of  the  elytra,  or  a  composite  of  the  ratios,  serve 
as  a  taxonomic  index  for  the  classification  of  the  species,  and,  together 
with  other  characters,  serve  to  distinguish  the  major  and  minor 
divisions  and,  to  a  certain  extent,  the  species.  The  progressive 
modification  appears  to  be  from  a  head  nearly  as  broad  as  the  pro- 
notum  and  the  latter  as  broad  as  the  elytra,  with  the  sides  nearly 
parallel,  to  a  head  much  narrower  than  the  pronotum,  the  latter 
slightly  narrower  than  the  elytra,  with  the  sides  narrowed  and  con- 
stricted toward  the  head;  also,  from  a  slender,  subelongate,  to  a 
stout  body. 

Color. — The  color  ranges  from  pale  yellowish-red  to  brown  and 
deep  black,  but  is  fairly  constant  in  the  matured  individuals  of  a 
species.  The  immature  individuals  are  always  lighter,  and  some  of 
those  of  the  black  species  are  reddish.  In  some  species  the  head, 
prothorax,  and  ventral  surface  of  the  body  are  darker  than  the 
elytra,  while  in  others  little  or  no  difference  is  noticeable. 

Vestiture. — The  body  is  more  or  less  clothed  with  short  to  long 
hairs,  the  presence  or  absence  of  which  on  different  areas  is  of  far 
more  taxonomic  significance  than  was  at  first  recognized.  Except 
in  old  rubbed  specimens,  the  vestiture  serves  as  one  of  the  important 
characters  distinguishing  the  major,  as  well  as  some  of  the  minor,  divis- 
ions. See  synopsis,  Divisions  I  and  II,  sections  al  and  a2  (PL  I) . 

Sculpture. — Within  the  genus  and  also  within  each  species  there 
is  considerable  variation  in  the  sculpture  of  the  front,  pronotum, 
and  elytra.  Nevertheless,  such  characters  as  the  presence  or  absence 


TIIK    (IKNTS.    DKNDKOrTONUS.  11 

of  frontal  grooves  and  tubercles  serve  to  distinguish  some  of  the 
minor  divisions  of  the  genus,  while  the  presence  or  absence  of  a 
posterior  median  impression  in  those  species  without  a  frontal  groove 
is  of  considerable  importance  in  "distinguishing  some  of  the  minor 
divisions.  The  relative  size,  density,  and  arrangement  of  the  punc- 
tures of  the  pronotum,  while  variable  within  the  species,  is  of  con- 
siderable taxonomic  value.  The  character  of  the  rugosities  of  the 
interspaces  and  the  punctures  of  the  striae  are  also  variable  within 
the  species  and  are  of  secondary  value  in  distinguishing  minor  divi- 
sions. The  sculpture  of  the  elytra!  declivity  is  of  special  specific 
and  sexual  importance,  and  in  some  cases  the  characters  are  of  value 
in  distinguishing  minor  divisions. 

THE    HEAD. 

The  general  characters  and  details  of  the  external  skeleton  and 
appendages  of  the  head  are  shown  in  figures  4,  5,  and  6.  It  will  be 
noted  that  the  elements  which  in  some  other  Coleoptera  and  other 
insects  are  more  or  less  clearly  defined  are  quite  completely  fused  and 
obscured  in  this  genus  as  in  other  rhynchophorous  beetles.  The 
labrum  and  clypeus  are  obsolete.  The  epistoma,  or  "post-clypeus," 
or  "pre-front,"  as  recognized  by  different  authors,  is  not  separated 
from  the  front  by  a  line  or  suture,  but  is  quite  clearly  defined,  and  the 
epistomal  process  is  far  more  prominent  than  in  other  allied  genera. 
The  front  is  completely  fused  with  the  epicranium,  which  in  turn  is 
fused  with  the  gense,  the  latter  joined  beneath  with  a  single  gular 
suture.  Anterior  to  the  gular  suture  there  are  three  quite  clearly 
defined  sclerites,  which  may  be  designated  as  pregula,  pregena,  and 
hypos toma  (fig.  5,  E).  By  comparing  the  head  of  Dendroctonus 
with  that  of  a  carabid  beetle,  Pterostichus  (fig.  7),  and  a  typical  curcu- 
lionid  beetle,  Pissodes  strobi  (figs.  8,  9),  the  striking  difference  in  struc- 
ture and  relative  position  of  the  corresponding  elements  and  their 
extreme  modification  are  at  once  apparent. 

Labrum. — The  labrum  is  not  present  as  a  distinct  element,  but  may 
be  represented  by  a  part  of  the  anterior  margin  of  the  epipharynx 
beneath  the  anterior  median  section  of  the  epistoma  (fig.  6,  A). 

Clypeus. — The  clypeus  is  not  represented  unless  it  is  by  the  pro- 
duced anterior  margin  of  the  epistoma,  and  by  the  long  epistomal 
bristles. 

Kpistoma  (figs.  2,  3,  4,  5,  6,  7,  10,  40,  B,  D,  E.)—  The  epistoma  is 
apparently  represented  in  both  the  larvae  and  adults  of  all  true  man- 
dibulate  insects,  but  is  more  distinctly  defined  in  some  than  in  others. 
In  some  insects  it  is  separated  from  the  clypeus  by  a  suture,  line,  or 
articulating  membrane,  while  in  others  there  is  no  evidence  of  sepa- 
ration or  the  clypeus  is  not  represented.  Its  separation  from  the 
front  is  often  defined  by  a  line,  impression,  elevation,  or  otherwise, 
although  sometimes  it  is  so  completely  fused  that  the  line  of  junction 


12 


THE   SCOLYTID   BEETLES. 


is  entirely  obscured,  as  in  Pterostictius.  It  serves  the  important 
function  of  a  rigid  bridge  over  the  oral  foramen  and  support  for  the 
clypeus,  labrum,  and  epipharynx,  and  at  its  lateral  angles  provides 
the  necessary  rigid  support  for  the  dorsal  articulation  of  the  man- 


Mandiblt 


eral  impression 


il axillary  palpus--^,  ^  \    ,, 


.Labial  palpu*/ 


Antennal  scrobe 


FIG.  4.—Dendroctonus  valens:  Head,  dorsal  and  lateral  aspects.  A ,  Dorsal  aspect  of  head;  B,  lateral  aspect 
of  head;  C,  dorsal  aspect  of  right  mandible;  D,  ventral  aspect  of  right  mandible;  c,  dorsal  area;  b,  dorsal 
impression;  c,  anterior  condyle;  d,  median  fossa;  e,  median  condyle;/,  posterior  fossa;  g,  basal  ridge;  ft, 
apical  tooth;  i,  acute  margin;,/,  subapical  tooth;  fc,  median  tooth;  I,  molar;  m,  anterior  condyle;  n,  me- 
dian fossa;  o,  posterior  condyle;  p,  lateral  area;  r,  dorsal  bristles  of  mandible;  s,  lateral  bristles  of  man- 
dible; t,  epistomal  bristles;  u,  lateral  angle  of  epistoma.  (Original.) 

dibles.  In  fact  the  latter  function  serves  to  distinguish  it  from  other 
parts.  The  median  area  is  variously  and  sometimes  greatly  modified 
in  insects  of  the  same  order  or  family,  and  it  appears  that  in  Coleop- 
tera  generally  this  element  is  of  much  greater  taxonomic  value  than 
has  been  usually  recognized  heretofore. 


THE   GENUS   DENDROCTONUS. 


13 


Epistomal  process. — In  Dendroctonus  the  epistomal  process  serves 
to  clearly  distinguish  the  genus  from  other  genera  of  the  suborder  to 
which  it  belongs.  This  process  is  usually  composed  of  a  median  and 


FIG.  5.— Dendroctonus  valens:  Head,  ventral  aspect,  and  mouthparts.  A,  Labimn;  B,  maxilla, interno- 
lateral  aspect;  C,  same,  externo-lateral  aspect;  D,  hypostomal  region,  dorsal  aspect;  E,  head,  ventral 
aspect;  a,  basal  fossa  of  mentum;  6,  joints;  c,  basal  membrane;  d,  palpiferal  area;  e.stipal  area;/,sub- 
galeal  area;  g,  fossa;  h,  muscle  processes;  k,  median  condyle;  I,  lateral  fossa;  TO,  anterior  condyle;  n, 
median  fossa;  o,  posterior  condyle;  p,  hypopharyngeal  bracon;  q,  submental  process;  r,  maxillary  con- 
dyle; s,  gular  apodeme;  u,  oral  foramen;  v.  occipital  apodeme;  w,  postgular  piece.  (Original.) 

two  lateral  sections  and  is  fringed  anteriorly  with  thickly  set,  long 
bristles  which  completely  cover  the  anterior  median  epistomal  area. 
Hypostoma  (fig.  5). — This,  as  here  interpreted,  is  a  ventral  piece 
or  area  which  corresponds  in  general  function  to  the  epistoma  in 
forming  a  rigid  ventral  rim  of  the  oral  foramen  for  the  support  of  the 


14 


THE   SCOLYTID   BEETLES. 


articulatory  accessories  of  the  labium  and  maxillae,  and  at  the  lateral 
angles  supports  the  ventral  articulations  for  the  mandibles.  It 
seems  to  the  writer  that  this  part  or  area,  whenever  sufficiently  dis- 
tinct to  be  recognized,  should  be  designated  as  the  hypostoma,  not 


Gular  suture* 


FIG.  ft.—Dendroctonus  valens:  Head,  oral  aspect,  epistoma,  etc.  A,  Ventral  aspect  of  epistomal  rogion; 
B,  dorsal  aspect  of  epistomal  region;  C,  oral  aspect  of  head;  c,  median  impression  and  longitudinal  ele- 
vations; 6,  median  condyle;  c,  lateral  fossa;  d,  posterior  fossa;  dd,  projection  over  median  condyle;  e, 
base  of  epistomal  bristles;  /,  median  section  of  epistomal  process;  ff,  lateral  angles  of  epistoma;  g,  ante- 
rior fossa;  h,  anterior  condyle  of  ventral  articulation;  i,  posterior  condyle  of  ventral  articulation  ;j,  median 
fossa  of  ventral  articulation;  fc,  hypopharyngeal  bracon;  I,  maxillary  condyle;  TO,  submental  processes; 
n,  ventral  view  of  hypopharynx;  o,  oral  foramen;  p,  dorsal  articulation  of  mandible;  q,  ventral  articu- 
lation of  mandible;  r,  apex  of  hypopharynx.  (Original.) 

on  account  of  any  theory  of  origin  from  a  primitive  segment,  but 

because  its  location  and  function  are  similar  to  those  of  the  epistoma. 

Front  (figs.  3,  4). — The  front  is  not  defined  by  sutures  or  lines,  but 

is  fused  anteriorly  with  the  epistoma  and  laterally  and  posteriorly  with 


THE   (iKM'S    DENDROCTONUS. 


15 


the  epicranium.  It  is  represented  by  a  frontal  area,  however,  which 
not  only  in  this  genus  but  in  other  scolytids  presents  characters  of 
special  value  in  distinguishing  major  and  minor  divisions,  species, 
sexes,  etc.  The  significance  of  frontal  characters  in  this  genus  is 
defined  in  the  synopses  of  adult  and  secondary  sexual  characters 
and  shown  in  trie  figures. 

AnttnnsR   (figs.    1-6,   11-13). — The  characters  of  the  antennae  are 
clearly  shown  in   the  figures.     The  scape,   funiculus,   and   club  are 


?.—  Pterostichus  californicus:  Head,  dorsal  and  ventral  aspects,  and  maxillae.  A,  Ventral  aspect;  B, 
dorsal  aspect;  C,  dorsal  aspect  of  left  maxilla;  D,  lateral  aspect  of  left  maxilla;  E,  ventral  aspect  of  left 
maxilla;  a,  stipal  foramen;  b,  muscle  processes;  c,  lacinial  digitus;  d,  cardo  fossa;  e,  basal  membrane; 
/,  palpiferal  bristle;  g,  stipal  bristle;  h,  median  fossa  of  ventral  articulation  of  mandible;  i,  labral  bristles; 
j,  clypeal  bristles.  (Original.) 

nearly  equal  in  length.  The  scape  toward  the  apex  is  clavate — cy- 
lindrical to  angular.  The  funiculus  is  5-jointed  and  always  slightly 
longer  than  the  club.  The  first  joint  (or  pedicel  of  some  authors)  is 
of  the  usual  form  and  as  long  or  longer,  rarely  shorter,  than  the 
second.  The  second  joint  is  as  long  as  the  third,  fourth,  and  fifth 
together,  or  slightly  shorter  in  some  species,  and  the  second  to  fifth 
increase  in  width  toward  the  club,  which  is  broad,  thickened  toward 
the  base  and  compressed  toward  the  apex,  and  has  three  or  four 
distinct  segments,  with  two  or  three  slightly  to  strongly  curved 


16 


THE   SCOLYTID  BEETLES. 


sutures.     The  relative  concavity  or  convexity  of  the  anterior  face, 
as  well  as  the  relative  lengths  of  the  segments  on  the  opposite  faces, 


Palpi 


Palpifer.., 
Mentum 


Occipital 


FIG.  S.—Pissodesstrobi:  Head,  vent  nil  aspect,  and  mouthparts.  A,  Ventral  aspect  of  apical  region  of  beak; 
B,  ventral  aspect  of  head;  r,  iult  rno-latcral  aspect  of  maxilla;  Z>,  externo-lateral  asp* ct  of  maxilla;  a, 
apical  tooth;  6,  subapical  tooth;  c,  lateral  arm  of  hypostoma;  d,  pleurostoma;  e,  mandibular  scrobe;/, 
hypostomal  area;  g,  lacinial  bristles;  h,  antennal  groove;  i,  joints;  j,  cardo  fossa;  k,  hypostomal  puncture. 
(Original.) 

contour  of  the  suture,  etc.,  are  shown  in  figures  11  to  13,  but  often 
appear  different  in  dried  specimens.     The  articulatory  attachment 


THE   GENUS  DENDROCTONUS. 


17 


of  the  scape  is  in  a  rather  deep  scrobe  (figs.  4,  5),  situated  in  front  of 
the  eye  near  the  base  of  the  mandible  and  lateral  angle  of  the  epistoma. 


Fi< ;. '.).  -Pissodes  strobi:  Head,  dorsal  aspect,  and  mandibles.  A ,  Dorsal  aspect  of  left  mandible;  B,  ventral 
aspect  of  left  mandible;  C,  dorsal  aspect  of  head;  a,  apical  tooth;  b,  subapical  tooth;  c,  median  tooth; 
d,  molar;  e,  median  condyle;/,  lateral  muscle  process;  g,  lateral  condyle;  h,  lateral  fossa;  i,  extensor  tendon; 
j,  pharyngeal  bracon;  k,  retractor  tendon;  I,  ventral  area;  m,  dorsal  area;  n,  median  condyle;  o,  anterior 
fossa;  p,  anterior  section  of  beak;  q,  posterior  section  of  beak;  s,  dorsal  area;  t ,  anterior  condyle;  u,  lateral 
fossa.  (Original.) 

Epicranium. — The  epicranium  is  not  defined  from  the  front  or  gena 
by  sutures  or  lines,  but  the  area  is  quite  clearly  indicated  by  the 


18  THE  SCOLYTID  BEETLES. 

smoother  surface  and  by  the  presence  of  the  compound  eye,  which  is 
situated  on  the  side  of  the  head  near  the  base  of  the  antennse.  The 
anterior  end  of  the  epicranial  suture  defines  the  anterior  dorsal  limit 
of  the  epicranium,  designated  as  the  vertex,  while  the  gena  is  repre- 
sented by  the  ventral  area  between  the  eyes  and  the  gular  suture. 
The  epicranial  suture  is  more  distinct  in  some  species  than  in  others. 

Eyes. — The  eyes  vary  from  slightly  oblong  oval  to  oblong  ovate 
and  are  obliquely  placed  in  the  anterior  angle  of  the  epicranial  area, 
just  posterior  to  the  base  of  the  antennae.  The  variation  in  form 
within  tlie  genus  and  within  the  same  species  is  shown  in  figures  1  to 
6  and  15.  There  are  about  four  hundred  facets,  which  are  small  and 
densely  placed. 

Occiput  (figs.  4,  5). — The  occiput  is  not  clearly  defined,  as  it  is  in 
Pterostichus ,  but  the  posterior  area  of  the  cranium  to  the  occipital 
foramen  may  be  designated  as  the  occipital  region  or  area. 

Occipital  foramen  (fig.  5). — The  posterior  opening  in  the  head,  or 
occipital  foramen,  is  small  as  compared  with  the  oral  foramen.  The 
invaginated  wall  forms  a  part  and  posterior  support  to  the  tentorium, 
and  the  dorsal  apodeme  is  continuous  with  the  epicranial  suture. 

Gula. — The  gula  is  not  represented  by  a  space  defined  by  two 
longitudinal  sutures,  as  in  most  Coleoptera  other  than  the  Rhyn- 
chophora.  The  gular  apodemes  are  present  (fig.  5,  D),  but  the  gular 
space  is  invaginated,  so  that  there  is  but  a  single  gular  suture. 

Pregula. — In  Dendroctonus  there  is  a  small  sclerite  immediately 
anterior  to  the  gular  suture  (figs.  5,  6)  which  is  distinctly  separated 
from  the  gula  and  gense  by  an  invaginated  apodeme,  laterally  from 
the  pregena  by  an  evident  exterr^al  line,  and  anteriorly  from  the 
hypostoma  by  a  ridge  which  defines  the  anterior  margin.  In  the 
rostrate  beetles  this  is  extended  with  the  pregena  and  forms  a  more 
or  less  distinct  gular  space  of  the  rostrum  to  a  similar  anterior  space 
which  supports  the  so-called  gular  peduncle,  or  submentum.  There- 
fore it  appears  that  the  term  pregula  should  serve  to  distinguish  this 
important  element,  which  is  also  more  or  less  distinctly  represented 
in  Coleoptera  other  than  the  Rhynchophora.  (Compare  figs.  6,  7,  8.) 

Gena. — The  gena  is  not  defined  by  lines,  but  it  is  represented  by 
the  ventral  area  between  the  gular  suture  and  the  epicranial  area, 
as  described  under  epicranium  and  gular  suture. 

Pregena  (figs.  5,  6). — The  pregena  is  a  distinct  pleural  area  situ- 
ated between  the  base  of  the  antennse  and  the  pregula,  bounded 
posteriorly  by  the  genal  area  and  anterior  angle  of  the  epicranium, 
and  anteriorly  by  the  hypostoma. 

Submentum  (figs.  5,  6). — The  submentum  is  represented  by  a 
bifid  process  or  median  extension  of  the  hypostoma,  and  is  sup- 
ported by  two  stout  braces  rising  from  the  large  transverse  rostral 
apodeme  beneath  the  posterior  angle  of  the  pregula. 


THE    GENUS   DENDROCTOXUS. 


19 


Labium  proper  (fiL'-  -  A  . — In  Demi  rod  on  us  and  other  rhyn- 
chophorous beetles,  the  mentum.  palpifer.  _  —  and  paragL  — 
while  more  or  less  clearly  indicated,  are  not  represented  as  separate 
elements  of  the  labium.  Mcniuvt:  The  mentum  articulates  with 
the  bifid  submentum  and  completely  surrounds  the  basal  portion  of 
the  labrum.  being  subcylindrioal,  with  the  anterior  ventral  area 

.illy  ret  use.  Palpifrr:  The  palpifer  is  represented  by  the  area 
between  the  ventral  impression  of  the  mentum  and  the  row  of 
palpiferal  bristles  winch  define  the  anterior  limit  of  the  mentum. 
Palpi:  The  labial  palpi  are  distinct,  3- jointed,  and  &s  long  as  the 
mentum,  or  longer,  with  the  first  joint  longer  than  the  other  two,  or 
rarely  equal.  Ligula:  The  ligula 

;ated  between  the  palpi,  is 

thickly  set  with  long  lacinial  teeth, 

and  occupies  the  greater  part  of 

the  dorsal   area.     It   is   evident 

that  this  ligular  area  represents 

-  :*?  and  paraglossa  of  other 

insects,  and   that  it    is  homolo- 

-  with  the  galea  and  lacinia 

of  the  first  maxilla. 

J/axtfl#(iL:     -       B,  C).— The 
maxilla?  (fig.  5,  B)  have  the  char- 

ist  ic  form  of  those  of  all  other 
rhynchophorous  beetles  and  are 
strikingly  different  from  those  of 
ot  her  Coleoptera .  The  form,  and 
relative  proportions  are  shown  in 
the  figures.  Cardo:  The  cardo  is 
the  stout  basal  section  which 
articulates  with  a  condyle  on 


FIG 


.^/)f  *drorto««L  Epistomaia.  «  to  / 
0'  D'  "l"pter  p  to  *'  D' 


t  he  maxillary  process  of  the  hy- 
inal  apodeme.  Stipes:  The 
stipes  articulates  with  the  cardo  and,  while  it  does  not  appear  as  a 
separate  piece,  it  is  represented  by  the  posterior  ventro-lateral  and 
externo-lateral  part  of  the  median  section  of  the  maxilla.  PaL 
golf  a,  subgalea,  and  lacinia:  The  palpifer  is  fused  with  the  stipes 
and  is  represented  by  the  anterior  part  of  the  median  section  (fig.  5). 
The  palpifer  and  stipes  are  also  fused  with  the  subgalea  on  the 
exto-lateral  area,  but  on  the  interno-lateral  area  the  line  separating 
the  palpifer  from  the  subgalea  is  distinct,  as  is  also  the  suture  be- 
n  the  latter  and  the  lacinia  and  galea,  which  are  fused,  the  latter 
being  represented  by  a  narrow  chitinous  margin  next  to  the  palpus 
and  palpifer.  The  lacinia  is  armed  on  the  inner  edge  with  stout 
lacinial  teeth.  The  length  of  the  base  of  the  subgalea  from  the  apex 


20 


THE   SCOLYTID   BEETLES. 


to  the  posterior  angle  is  usually  greater  than  the  length  of  the  palpifer 
and  stipes,  but  is  sometimes  equal  and  rarely  shorter.     The  ventral 


FIG.  ll.—Dendroctonus:  Antennae.  1,  brevicomis;  3,  convexifrons  9;  3a,  convexifrons  tf;  4,frontalis  J1;  5, 

arizonicus  cf;  5a,arizonicus  9;  6 ,  mexicanus;  7 ,  parallelocollis;  8,approximatus  9.    (Original.) 

I—a,  posteriorface  of  club  when  antenna  is  extended  at  right  angles  to  head,  joints  1,  2,  3;  6,  anterior  face, 

joints  1,  2,  3,  4;  d,  funiculus,  joints  1,  2,  3,  4,  5;  c,  scape. 

chitinous  area  of  the  palpifer  and  stipes  together  is  always  a  third 
or  more  longer  than  the  combined  chitinous  parts  of  the  joints  of 


FIG.  12, — Dendroctonus:  Antennse.    9,  monticolse;  10,  ponderosse;  12,  simplex;  13,  pseudotsugx  9 ; 
perda  9 ;  15,  engelmanni;  17,  obesus  tf;  17a,  obesus  9.    (Original.) 

the  palpi.  Palpi:  The  palpi  are  3-jointed;  the  joints  connected 
with  each  other  and  with  the  palpifer  by  flexible  membrane  which 
allows  for  a  certain  amount  of  telescoping,  but  not  adapted  for  free 


THE   GENUS   DENDROCTONUS. 


21 


lateral  movements  as  in  Pterostichus  (fig.  7).  The  relative  lengths 
of  the  joints  vary  considerably  in  the  species  of  the  genus,  and  more 
or  less  in  the  individuals  of  a  species.  The  first  joint  is  usually 
longer  than  the  other  two  together,  but  is  sometimes  equal  or  shorter; 
the  second  joint  is  usually  longer  than  the  third,  but  is  sometimes 
shorter. 

Mandibles  (figs.  4,  14). — The  mandibles  are  prominent,  stout, 
triangular,  and  especially  adapted  for  burrowing  in  the  bark.  The 
inner  edges  are  acute,  with  a  subapical  and  a  median  tooth  toward 
the  middle  and  a  molar  on  the  basal  .angle.  The  lateral  area  toward 
the  base  has  a  large  impression  and  there  is  usually  a  less  evident 
one  on  the  dorsal  area,  each  bearing  one  or  two  bristles.  The  dorsal 


FIG.  13.—Dendroctonu$:  Antennae.    18,  rufipennis;  20,  punctatus;  21,  micans;  22,  terebrans;  23,  valens  J; 
23a,  valens  9;  23b,  valens  <?;  23c,  valens  9.    (Original.) 

articulation  with  the  epistoma  is  especially  adapted  to  meet  its 
several  requirements.  The  peculiar  trochlear  mechanism  of  the 
articulating  condyles  and  fossa  are  illustrated  in  figure  14;  that  of 
the  dorsal  condyle  appears  to  be  common  to  other  rhynchophorous 
beetles,  but  apparently  not  represented  in  other  Coleoptera,  including 
those  with  similar  bark  and  wood  boring  habits.  The  ventral 
articulation  also  appears  to  be  different  from  that  in  other  Coleop- 
tera, but  to  a  less  degree.  A  detailed  comparative  study  of  the 
mandibles  may  reveal  specific  characters,  but  as  a  rule  such  charac- 
ters are  unsatisfactory  from  the  fact  that  in  comparisons  the  man- 
dible must  be  viewed  from  exactly  the  same  position  to  avoid  error 
in  conclusions. 


22 


THE  SCOLYTID  BEETLES. 
THE  THORAX. 


The  thorax,  as  usual,  consists  of  three  distinct  segments.  The 
prothorax  freely  articulates  with  the  mesothorax,  but  the  pleurites 
and  sternites  of  the  mesothorax  and  metathorax  are  rigidly  con- 
nected. The  combined  length  of  the  ventral  areas  of  the  three 
thoracic  segments  is  slightly  greater  than  that  of  the  ventral  area  of 
the  abdominal  segments,  while  the  combined  length  of  the  dorsal 


FIG.  14. — Dendroctonus  valens:  Mandible,  a,  Apical  tooth;  b,  subapical  tooth;  c,  median  tooth;  d, 
molar  tooth;  e,  dorsal  area;  /,  dorsal  bristles  or  setae;  g,  dorsal  impression;  h,  transverse  ridgs;  i,  pha- 
ryngeal  process;  j,  retractor  tendon;  fc,  lateral  area;  I,  lateral  bristle;  m,  lateral  impression;  n,  anterior 
condyle;  o,  basal  ridge;  p,  median  fossa;  q,  median  condyle;  r,  posterior  fossa;  s,  condyle  of  ventral 
articulation;  t,  basal  foramen;  u,  retractor  disk;  v,  extensor  disk;  w,  extensor  tendon.  (Original.) 

areas  of  the  thoracic  segments  is  about  equal  to  that  of  the  area  of 
the  abdominal  segments,  or  slightly  longer.  The  pronotum  is  as 
long  as  both  the  mesotergum  and  the  metatergum  together.  The 
prosterna  and  mesosterna  are  about  equal  in  length,  and  both 
together  about  equal  to  the  metasterna,  while  the  combined  length 
of  the  thoracic  pleura  is  slightly  greater  than  that  of  the  abdominal 
pleura.  The  anterior  dorsal  margin  of  the  pronotum  and  the  pos- 
terior margin  of  the  metatergum  are  greatly  extended  anteriorly 


THE   GENUS   DENDROCTONUS. 


23 


beyond  the  ventral  margin  of  the  same  segments,  while  the  posterior 
dorsal  margin  of  the  pronotum  and  the  anterior  dorsal  margin  of  the 
mesonotum  are  not  produced  beyond 
the  corresponding  sternal  margin. 

DIVISIONS  OF  THE  THORACIC  SEGMENT. 


The  divisions  and  other  characters 
peculiar  to  the  thoracic  segments  of  a 
scolytid  beetle  are  shown  in  figures  16, 
17,  18,  19,  and  20. 

It  will  be  noted  that  while  the  usual 
divisions  or  sclerites  are  quite  clearly  de- 
fined in  the  metathorax,  corresponding 
divisions  are  less  distinct  in  the  mesotho- 
rax,  and  are  obsolete  or  completely  fused 
in  the  prothorax.  The  taxonomic  signifi- 
cance of  this  wide  range  in  the  modifica- 
tion of  similar  parts  or  areas  in  the  three 
thoracic  segments  of  the  same  insect  is 
realized  when  we  compare  these  parts 
with  corresponding  segments  in  repre- 
sentative species  of  other  families,  sub- 
orders, and  orders  of  insects.  It  will  be  seen  that  each  segment  has 
characters  peculiar  to  the  order  or  minor  group  to  which  the  species 

belongs,  and  that  in  like 
manner  the 
characters  of 
or  all  three  in  the  same 
insect  present  many  fea- 
tures peculiar  to  the  groups, 
the  suborder,  family,  genus, 
or  species  represented. 

It  is  also  significant  of 
the  influence  of  a  domi- 


B 


FIG.  15.—Dendroctonus:  Eyes.  1,  brevi- 
comis;  2,  barberi;  5,  arizonicus;  8,  ap- 
proximatus;  10,  Wa,  ponderosx;  12, 
simplex;  18,  pseudotsugx;  14,  piceaperda; 
15,  15a,  engelmanni;  20,  punctatus;  22, 
22a,  b,  c,  terebrans;  23,  23a,  b,  c,  d,  e,f, 
g,  h,  i,  j,  k,  I,  valens.  (Original.) 


combined 
any     two 


nant  principle  or  plan  of 
structure  and  order  of  mod- 
ification that  one  or  more 
thoracic  segments  of  prac- 
tically any  insect  examined 
will  show  certain  divisions 
more  or  less  clearly  defined, 
which  are  common  to  all 
other  insects,  and  that 
when  we  compare  the  segments  of  different  stages  of  insects  of  all 
orders,  we  find  that  a  composite  segment  would  represent  a  system 
of  four  longitudinal  and  four  transverse  divisions.  The  longitudinal 


FIG.  16. — Dendroctonus  valens:  Areas  of  pronotum.  A,  an- 
terior area;  B,  median  area;  C,  posterior  area;  D,  lateral 
area;  E,  dorsal  area;  a,  anterior  angle;  aa,  anterior  margin; 
6,  posterior  angle;  d,  basal  margin;  e,  posterior  declivity; 
/,  anterior  section  of  lateral  area;  g,  anterior  section  of  dorsal 
area;  h,  median  section  of  lateral  area;  i,  median  section  of 
dorsal  area;  j,  posterior  section  of  lateral  area;  k,  posterior 
section  of  dorsal  area;  I,  posterior  margin  or  vertex. 
(Original.) 


24 


THE   SCOLYTID   BEETLES. 


reHpiaternal  area 
•Prestcmal  area 

-Sternal  area 
E  piste  rnal  area 
,  Intercoxal  or 
"stemellar  area 
^E.wcoxal  area 

Epimeral  area 


^Poststernellar  area 

FIG.  17.— Dendroctonus  valens:  Areas  of  prothorax,  ventral 
aspect,  a,  Anterior  margin;  6,  posterior  margin;  c,  an- 
terior angle;  d ,  posterior  angle;  e,  anterior  entothoracic 
fold  for  attachment  of  intersegmental  membrane;  /,  an- 
terior foramen;  g,  posterior  foramen;  h,  coxal  cavity. 
(Original.) 


divisions  are  one  dorsal,  two  lateral,  and  one  ventral;  the  transverse 
divisions  are  one  anterior,  two  median,  and  one  posterior. 

Audouin  (1824)  recognized  the  four  longitudinal  divisions  and 
named  them  sternum,  pleurae,  and  tergum.  He  also  recognized  two 
divisions  of  the  pleura  and  named  them  episternum  and  epimerum, 
and  four  transverse  divisions  of  the  tergum,  which  he  named  pres- 

cutum,  scutum,  scutellum, 
and  postscutellum.  These 
names  have  been  adopted 
with  but  slight  modifica- 
tion by  most  of  the  leading 
writers  on  insect  anatomy, 
including  McLeay,  1830; 
Newport,  1839;  Kolbe, 
1889;  Amans,  1885;  Corn- 
stock,  1902;  and  Voss, 
1905.  The  same  divisions 
have  been  recognized  by 
many  other  authors,  who 
have  designated  them  by 
different  names. 

The  first,  second,  third,  and  fourth  transverse  divisions  of  the 
ventral  or  sternal  area  were  recognized  by  McLeay  in  1830,  and 
named,  in  order,  presternum,  sternum,  sternellum,  and  poststernellum. 
All  of  the  divisions  and  subdivisions  mentioned  as  having  been 
recognized  by  Audouin  and  McLeay  are  here  recognized  by  the  writer, 
and,  in  addition,  the  first  and  fourth  transverse  divisions  of  the  pleura; 
thus  four  longitudinal  and  four 

transverse    divisions    of    each  SN     Presternum 

segment  in  the  adult  insect 
have  been  recognized.  The 
writer  has  also  recognized  the 
same  or  a  similar  system  of 
division  in  the  thoracic  and 
abdominal  segments  of  larvaB 
and  pupae.  While  the  taxo- 
nomic  significance  of  the  char- 
acter and  modification  of  these 
primary  and  secondary  divisions  as  represented  in  one  or  more  thoracic 
segments  of  the  same  insect,  or  in  one  or  more  segments  in  insects  of 
different  orders  and  minor  groups,  has  been  recognized,  there  has  been 
wide  difference  of  opinion  as  to  the  origin  or  homology  of  these  divisions 
and  in  their  interpretation  or  definition.  This  has  naturally  resulted 
in  much  confusion  in  the  adoption  and  application  of  the  nomencla- 
ture proposed  by  different  authors,  and,  more  than  anything  else 


\^,-Precpi  sternum 
—b 


ISternellar  area''      f 
Poststemellar  piece' 

FIG.  18. — Dendroctonus  valens:  Mesothorax,  ventral 
aspect,  a,  Preepisternal  process;  b,  transverse  im- 
pression; c,  coxal  cavity.  (Original.) 


THE   GENUS  DENDROCTONUS.  25- 

connected  with  the  anatomical  problem,  it  was  this  state  of  confusion 
which  led  the  writer  to  make  a  study  of  the  subject  in  order  to  deter- 
mine the  facts  and  principles  involved  and  to  establish  a  basis  for 
his  future  systematic  and  economic  work  on  the  scolytid  and  other 
beetles. 

There  appear  to  be  two  opposing  ideas  regarding  the  origin  and 
evolution  of  the  primary  and  secondary  elements  of  the  insect  seg- 
ment. One  involves  the  principle  of  reduction  of  several  primitive 
segments  into  one,  on  the  theory  that  the  transverse  divisions  rep- 
resent modifications  of  several  primitive  segments.  The  other  involves 
the  principle  of  complex  modification  from  a  simple  undivided  primi- 
tive segment  into  many  primary  and  secondary  divisions,  on  the 
theory  that  this  has  been  brought  about  more  or  less  independently 
through  the  influence  of  the  requirements  of  function  to  meet  the 
demands  of  peculiar  life  activity  in  different  forms  or  species,  and 
that  this  plan  of  modification  has  been  controlled  and  limited  by 
the  fundamental  plan  of  structure  in  the  hexapodal  type  of  organism, 
and  by  the  principle  of  relative  proportions  and  correlation  of  parts 
so  as  to  conform  to  the  general  modification  of  the  entire  body  in 
the  evolution  of  the  species. 

The  writer  does  not  deem  it  advisable,  in  this  connection,  to  dis- 
cuss the  relative  merits  of  these  theories  or  any  of  the  other  theories 
advanced  by  different  authors.  He  is  inclined  to  believe  that  while 
it  is  important  to  utilize  any  good  evidence  relating  to  the  probable 
origin  and  homology  of  parts,  it  is  more  important  for  present  needs 
to  deal  with  the  facts  as  they  are  found  in  existing  forms  and  stages 
and  to  so  name  and  define  the  major  and  minor  divisions  or  elements 
of  the  segment  that  they  may  be  readily  recognized  and  utilized  in 
any  comparative  study  of  their  modification  and  in  the  description 
and  identification  of  species,  genera,  and  larger  groups.  Therefore 
the  writer's  interpretation  of  the  recognizable  elements  in  the  thoracic 
segments  of  Dendroctonus  does  not  involve  any  theory  of  origin  or 
evolution,  but  is  based  on  the  recognition  of  a  dominant  tendency 
in  the  insect  segment  to  represent  a  system  of  four  longitudinal  and 
four  transverse  divisions,  any  one  or  all  of  which  may  or  may  not  be 
clearly  represented  in  one  or  more  segments  of  the  same  insect. 

With  this  conception  of  a  prevailing  principle  as  a  guide  to  the 
location  of  the  possible  primary  and  secondary  divisions  of  the  ana- 
tomical elements  as  they  are  indicated  in  any  given  segment,  and  to 
the  recognition  of  the  possible  range  of  modification  and  distinction 
as  manifested  in  the  different  segments  of  the  same  insect  or  in  the 
corresponding  segment  of  different  insects,  many  of  the  difficulties 
and  confusing  factors  relating  to  the  proper  definition  of  parts  and 
application  of  names  are  eliminated. 


26  THE  SCOLYTID  BEETLES. 

In  the  following  discussion  of  the  thoracic  segments  reference  is 
made  to  the  named  parts  as  represented  or  not  represented,  as  the  case 
may  be,  rather  than  to  say  that  they  are  present  or  not  present, 
because  in  some  cases  where  they  are  not  defined  on  the  external 
surface  they  may  be  indicated  by  apodemes  or  lines  on  the  inner 
surface  of  the  body  wall,  while  in  other  cases  their  position  or  rela- 
tive areas  are  indicated  only  by  some  character  of  surface  sculpture 
or  vestiture. 

In  the  adult  Dendroctonus  there  is  a  wide  range  of  difference  in  the 
representation  of  parts  in  the  prothorax,  mesothorax,  and  meta- 
thorax.  In  the  pupa  there  is  a  similar  but  not  so  marked  difference 
between  the  three  thoracic  segments,  the  divisions  being  less  evident 
in  the  mesothorax  and  metathorax  than  in  the  adult,  but  in  the 
abdominal  tergites  the  divisions  are  quite  plainly  indicated.  In  the 
larvae  there  is  not  only  less  difference  in  the  three  thoracic  segments, 
but  these  are  only  slightly  different  from  the  first  to  seventh  abdomi- 
nal segments.  In  the  thoracic  segments  the  present al  and  scutel- 
lar  divisions  are  clearly  represented,  with  evidence  of  the  scutal  divi- 
sion on  the  sides.  The  sternal  and  sternellar  divisions  are  also 
clearly  represented,  with  evidences  of  the  presternal  and  poststernellar 
divisions  in  the  prosternum,  and  the  latter  clearly  defined  in  the 
mesosternum  and  metasternum.  The  pleurites  are  also  represented 
by  pleural  lobes.  In  the  abdominal  tergites  1  to  6  the  prescutal, 
scutal,  and  scutellar  divisions  are  clearly  represented  and  the  sternal, 
sternellar,  and  poststernellar  divisions  are  in  like  manner  repre- 
sented in  abdominal  sternites  1  to  8,  inclusive.  Whether  or  not  these 
divisions  or  lobes  are  homologous  with  divisions  occupying  rela- 
tively the  same  positions  in  the  pupa  and  adult  may  be  a  subject  for 
difference  of  opinion,  but  the  names  here  applied  to  what  appear  to 
be  corresponding  parts  should  serve  as  a  reliable  guide  to  their  recog- 
nition and  accurate  definition  and  description  in  comparative  studies 
and  identification  of  species. 

ELEMENTS  OP  THE  ADULT  THORAX. 

The  primary  and  secondary  elements  as  represented  in  the  thoracic 
segments  of  an  adult  Dendroctonus  beetle  are  shown  in  the  figures 
and  are  interpreted,  named,  and  described  as  follows  :a 

THE  PROTHORAX. 

In  this  genus,  as  in  rhynchophorous  beetles  generally,  the  tergal, 
pleural,  and  sternal  areas  are  fused  into  a  continuous  band.  The 

a  Notum  and  tergum. — While  the  names  notum  and  tergum  are  synonymous,  the 
former  has  been  applied  more  specifically  to  the  dorsal  division  of  the  prothorax, 
especially  in  beetles,  and  is  here  utilized  in  that  sense.  The  name  tergum  is  here 
used  to  designate  the  dorsal  areas  of  the  mesothorax,  metathorax,  and  abdomen,  on 
account  of  the  use  of  the  term  tergite  to  designate  a  subdivision. 


THE   GENUS  DENDROCTONUS.  27 

primary  and  secondary  divisions  are  not  indicated  by  lines  or  sutures, 
but  the  corresponding  areas  are  suggested  by  peculiar  characters  of 
sculpture  and  vestiture,  which  are  of  more  or  less  taxonomic  impor- 
tance, and  thus  may  be  arbitrarily  indicated,  as  in  figures  16  and  17, 
to  serve  as  guides  to  the  location  of  characters  in  comparative  study 
and  description. 

Pronotum. — The  pronotum  is  the  dorsal  or  tergal  area  of  the  pro- 
thorax,  as  defined  by  the  anterior,  posterior,  and  lateral  margins. 
There  is  considerable  specific  variation  in  its  structure,  sculpture,  and 
relative  proportions.  It  ranges  from  about  one-fourth  to  about  one- 
third  broader  than  long,  with  about  the  same  range  of  difference  in 
the  width  of  the  posterior  and  anterior  areas.  In  some  species  the 
lateral  margins  are  nearly  parallel,  while  in  others  they  are  distinctly 
convergent  and  constricted  anteriorly.  The  anterior  margin  is 
broadly  sinuate,  while  the  vertex  or  dorsal  margin  of  the  posterior 
declivity  is  bisinuate.  The  anterior  area  is  broadly  transversely 
impressed,  except  in  the  females  of  some  species,  where  the  median 
section  of  the  area  is  transversely  elevated.  The  posterior  declivity, 
which  perhaps  represents  the  postscutellum,  is  more  distinctly 
exposed  and  defined  in  this  genus  than  it  is  in  allied  genera  and  is 
therefore  an  important  character  of  generic  distinction.  The  pleural 
and  sternal  areas  are  indicated  in  figure  17. 

Episternal  area. — The  episternal  area  is  limited  dorsally  by  the 
lateral  margins  of  the  notum,  ventrally  by  the  smooth  exocoxal 
area,  posteriorly  by  the  epimeral  area,  and  anteriorly  by  a  preepis- 
ternal  impression  or  in  some  species  by  a  ridge.  The  sculpture  of 
this  area  is  quite  variable  and  in  some  species  furnishes  characters  of 
considerable  value. 

Epimeral  area. — The  epimeral  area  is  represented  by  a  flattened, 
smooth  space  situated  between  the  roughened  episternal  area  and  the 
posterior  margin  of  the  prothorax  and  between  the  coxae  and  the 
basal  angle  of  the  notal  area. 

Sternal  area. — The  entire  sternal  area  between  the  anterior  and 
basal  margins  is  largely  occupied  by  the  coxal  cavities,  which  are 
separated  by  the  very  narrow  intercoxal  or  sternellar  piece.  The 
elevated  anterior  margin  evidently  represents  the  presternum,  while 
the  sternum  is  quite  clearly  defined  by  a  nearly  vertical  flat  to  con- 
cave space  between  the  presternum  and  the  coxse,  the  lateral  limit 
being  indicated  by  the  smooth,  shiny  exocoxal  area  between  the  coxae 
and  the  episternal  area.  The  sternum  proper  is  quite  variable,  rang- 
ing from  concave,  smooth,  and  shiny,  without  trace  of  a  median  lon- 
gitudinal line  to  nearly  flat,  roughened,  or  with  a  median  subcari- 
nate  line;  but  apparently  none  of  these  minor  characters  is  suffi- 
ciently constant,  even  within  the  same  species,  to  be  of  much  taxo- 
nomic value. 


28 


THE    SCOLYTID   BEETLES. 


Poststernellar  area — The  poststernellar  area  is  well  defined  and 
serves  to  completely  inclose  the  coxal  cavity.  It  has  been  referred 
to  as  the  epimeron,  but  since  the  epimeral  is  so  clearly  defined  as  a 
lateral  area,  it  appears  to  more  correctly  represent  the  poststernellum, 
which  in  the  mesosternum  and  metasternum  is  not  evident,  or  is 
modified  to  accommodate  the  large  coxal  cavities. 

THE  MESOTHORAX. 

The  mesothorax  (figs.  18,  19)  is  short  and  partially  hidden 
from  view  by  the  prothorax,  which  covers  the  anterior  third  of  the 
sterna,  pleurites,  and  tergites,  while  the  base  of  the  elytra  covers 


Teryites 


FIG.  19. — Dendroctonus  valens:  Mesotergum  and  mesopleurum.  a,  Lateral  arm  of  prephragma  and 
prescutum;  6,  wing  root  or  connecting  membrane;  c,  tasal  margin  of  elytra;  d,  radial  plate;  e,  flexor 
plate;  /,  median  plate;  g,  scapular  plate;  h,  subscapular  plate;  i,  sutural  or  anal  margin;  j,  preepisternal 
process;  fc,  clavicle  condyle;  I,  coracoidal  condyle;  m,  scutellum;  n,  lateral  margin  of  elytra;  o,  arm  of 
preepisternal  process;  striae  2-10;  interspaces  2-11;  p,  lateral  arm  of  postphragma;  q,  pleural  claviculus. 
(Original.) 

the  posterior  third  and  dorsal  area  of  the  tergum,  leaving  but  a 
small  triangular  area  exposed  between  the  thorax  and  inner  angles 
of  the  elytra.  Upon  removing  the  prothorax  and  elytra  this  segment 
is  found  to  represent  most  of  the  primary  and  secondary  divisions 
of  the  normal  segment. 

MESOTERGUM. 

The  mesotergum  (fig.  19)  is  rectangular  in  form,  with  the  pre- 
scutum occupying  two-thirds  of  the  area,  while  the  scutum,  scutellum, 
and  postscutellum  are  less  clearly  defined  or  rudimentary. 

Prescutum. — It  is  evident  that  the  large  subtriangular  dorsal  sec- 
tion represents  the  prescutum,  as  indicated  by  the  evident  prescutal 
lobe  and  prescutal  process,  attachment  of  wing  accessories,  etc. 


THE   GENUS   DENDROCTONUS.  29 

Prephragma. — The  prephragma  is  strongly  flexed  beneath  the 
median  area,  but  the  anterior  arms,  in  conjunction  with  the  anterior 
angles  of  the  prescutum,  are  prominent  and  strongly  produced. 

Scutum. — The  oblique,  impressed,  triangular  section  situated 
beneath  the  posterior  margin  of  the  prescutum  evidently  represents 
the  scutum. 

Scutellum. — The  hornlike  process  situated  at  the  apical  angle  of 
the  prescutum  apparently  belongs  to  the  scutellum  and  corresponds, 
perhaps,  to  the  structure  which  forms  the  scutellar  groove  of  the 
metathorax.  This,  with  the  posterior  lateral  section,  represents  the 
median  and  lateral  sections  of  the  scutellum. 

PostscuteUum. — The  postscutellum  apparently  is  not  represented 
by  an  external  piece,  but  by  an  evaginated  fold  beneath  the  scutellum 
and  by  the  lateral  arms  of  the  postphragma  (fig.  19). 

Postphragma. — The  postphragma  is  represented  by  the  posterior 
invagination  or  fold  beneath  the  scutellum  and  by  the  lateral  arms, 
as  evidenced  by  the  attachment  of  the  scutal  muscle  to  the  arm  and 
the  connection  of  the  arm  with  the  invaginated  phragma. 


MESOPLEURA. 


The  episternum,  preepisternum,  epimerum,  and  postepimerum  are 
all  represented  and  together  occupy  an  area  greater  than  that  of  the 
sternal  and  slightly  greater  than  that  of  the  tergal. 

Preepisternum. — The  preepisternum  occupies  the  area  in  front  of 
a  transverse  impression  and  is  quite  prominent.  The  anterior  mar- 
gin bears  the  preepisternal  process  (fig.  19,  j),  which  is  common  to 
most  of  the  Khynchophora,  and  is  more  or  less  represented  in  certain 
other  Coleoptera,  such  as  Carabidae,  Cicindelidae,  Scarabseidae,  etc., 
but  it  is  surprising  to  find  that  it  is  not  represented  in  Ips  ( Tomicus) 
and  allied  genera  of  the  Scolytidae.  It  is  peculiar  to  the  mesothorax 
and  is  progressively  modified  in  character  and  function  through 
various  groups  of  Coleoptera  from  an  obscure  accessory  of  the  clavi- 
cle disk  to  a  prominent  process.  In  Dendroctonus  it  is  fused  with 
the  anterior  margin  of  the  preepisternum  and  has  an  arm  extending 
to  the  dorsal  angle  to  form  an  accessory  to  the  wing  process.  It 
bears  a  set  of  powerful  muscles,  which  are  attached  to  the  inner  wall 
of  the  postscutellar  and  scutellar  areas  of  the  pronotum,  thus  form- 
ing a  powerful  muscle  connection  between  the  two  segments.  The 
mesothoracic  spiracle  is  situated  in  the  angle  between  this  process 
and  the  sternal  area  and  is  covered  by  the  epicranial  area  of  the 
prothorax. 

Clavicle  disk. — The  slender  plate  situated  in  front  of  the  arm  of 
the  preepisternal  process  appears  to  correspond  with  the  clavicle 
disk  of  the  metapleurum.  It  is  connected  by  a  ligament  to  the  head 
of  the  elytra,  and  its  muscle  is  attached  to  the  rudimentary  ante- 
coxal  piece.  Both  the  preepisternal  process  and  the  clavicle  plate, 


30  THE  SCOLYTID  BEETLES. 

as  here  defined,  are  probably  modifications  of  the  episternal  paraptera 
of  Audouin. 

Episternum. — The  episternum  is  the  clearly  defined,  large,  exposed 
triangular  pleurite  situated  between  the  posterior  margin  of  the 
preepisternum  and  the  epimerum,  with  the  dorsal  angle  dilated,  pro- 
duced, and  flexed  ventrally  at  the  apex  and  with  the  apex  of  the 
epimerum  and  preepisternal  process  forming  the  pleural  claviculus 
with  its  clavicle  and  coracoidal  condyle  for  the  articulation  of  the 
elytra.  The  posterior  angle  of  the  episternum  is  acute,  and  the 
suture  between  it  and  the  sternum  is  obliquely  sinuate.  The  epi- 
sternal impression  is  clearly  defined  by  the  elevated  posterior  margin 
of  the  preepisternum,  and  is  usually  covered  by  the  posterior  margin 
of  the  prothorax. 

Epimerum. — The  epimerum  is  exposed  at  its  posterior  ventral 
half  and  has  its  posterior  margin  fused  with  the  metasternum  and 
metepisternum  and  the  produced  anterior  dorsal  angle  with  its 
coracoidal  condyle  is  covered  by  the  episternum. 

Postepimerum. — The  postepimerum  is  represented  by  a  small  de- 
clivous area  beneath  the  posterior  dorsal  angle,  where  it  covers  the 
metathoracic  spiracle. 

MESOSTERNA. 

Presternum  (fig.  18). — The  presternum  is  quite  clearly  represented 
by  the  narrow,  slightly  elevated,  anterior  margin  joined  directly  with 
the  anterior  ventral  angle  of  the  preepisternum. 

Sternum. — The  sternum  is  short,  flat,  and  subdeclivous,  with  the 
posterior  angle  (exocoxal  piece)  extending  around  the  coxal  cavity  to 
its  junction  with  the  anterior  angle  of  the  metasternum. 

Sternellar  area. — The  sternellar  area  appears  to  be  represented  by 
the  elevated  and  rather  broad  intercoxal  piece,  while  the  poststernel- 
lum  is  apparently  represented  by  a  poststernellar  piece. 

THE  METATHORAX. 
METATERGUM. 

From  a  systematic  and  taxonomic  point  of  view,  the  metatergum 
is  by  far  the  most  important  and  interesting  part  of  the  thorax  of 
beetles.  We  find  in  it  not  only  evidence  of  the  four  transverse 
divisions,  but  examples  of  the  possible  extremes  in  modification  to 
meet  the  requirements  of  wing  articulation  and  wing  motion. 

Transverse  sutures. — By  a  comparison  of  the  metatergum  of  repre- 
sentatives of  different  orders  of  insects  and  of  the  larvae,  pupae,  and 
adults  of  some  insects,  as  in  Dendroctonus,  we  find  that  the  prevailing 
principle  of  division  involves  three  transverse  external  lines,  sutures, 
or  impressions,  and  three  corresponding  entothoracic  ridges,  apo- 
demes,  or  invaginated  ectoderm,  which  define  more  or  less  clearly 
the  four  divisions,  viz,  prescutum,  scutum,  scutellum,  and  postscu- 


THE   GENUS   DENDROCTONUS. 


31 


tellum.     We  also  find  that  these  transverse  sutures  are  subject  to 
great  variation  in  position,  contour,  character  of  surface,  manifesta- 


; Lateral  emarginalion 

P,-c»:ulal  process  • — 

lal  dine  — 
.--'Pr&culat 


FIG.  2Q.—Dendroctonus  valens:  Metatergum  and  metapleunim.  B,  Anterior  aspect  of  prephragma  and 
prescutum;  D,  metatergum  and  inetapleurum;  E,  posterior  aspect  of  postphragma  and  postscutel' 
him;  a,  lateral  arm  of  prephragma;  6,  dorsal  band;  c,  scapular  plate;  d,  subscapular  plate;  e,  flexor 
plate;  /,  radial  plate;  g,  medial  plate;  ft,  lateral  arm  of  postphragma;  i-i,  metatergal  costse;  j,  anterior 
disk;  k,  scutellar  groove;  I,  posterior  ridge;  o,  exposed  triangular  plate  of  postepimeron;  p,  pleural 
hinge;  pc,  pleural  clavicula;  q,  posterior  ventral  angle  of  episternum;  r,  anterior  ventral  angle  of 
episternum;  s,  pleural  suture;  t,  postscutellar  process;  u,  clavicle  condyle;  v,  coracoidal  condyle; 
w,  attachment  and  articulation  of  scapular  plate;  x,  dorsal  area  of  postscu tellum;  y,  pleural  disk; 
z,  elevated  acute  margin;  zl,  membranous  area;  z2,  villous  area.  Wing  veins:  C,  costa;  5c,sub- 
costa;  R,  radius;  M,  media;  Cu  1,  cubitus  1;  Cu  2,  cubitus  2;  A,  anal.  (Original.) 

tions,  etc.,  to  correspond  with  the  enormous  range  of  modification  to 
which  one  or  all  four  of  the  transverse  divisions  are  subject.  These 
external  evidences  of  separation  of  parts  are  here  referred  to  as  sutures, 


32  THE  SCOLYTID  BEETLES. 

although  in  some  cases  they  may  be  but  faintly  or  obscurely  indicated. 
The  lateral  and  median  sections  of  the  anterior  suture  separating  the 
prescutum  from  the  scutum  have  a  tendency  to  curve  posteriorly, 
and  especially  the  median  section,  which  has  a  very  strong  tendency 
in  this  direction,  and  is  often  manifested  to  such  an  extent  as  tot 
separate  the  scutum  into  two  lateral  sections,  as  shown  in  figure  20. 
The  median  suture  has  a  reverse  tendency,  the  lateral  sections 
extending  anteriorly,  the  submedian  section  posteriorly,  and  the 
median  strongly  anteriorly.  Thus  we  often  find,  as  shown  in  figures 
20  and  21,  that  the  two  sutures  overlap  and  form  external  longitu- 
dinal ridges  and  internal  oblique  apodemes,  with  an  external  median 
longitudinal  impressed  area.  It  appears  that  the  dorsal  groove  may 
belong  to  either  the  scutellum  or  prescutum  or  represent  a  combina- 
tion of  the  two,  but  for  the  sake  of  uniformity  in  its  definition  the 
name  scutellar  groove  is  here  adopted.  The  posterior  suture  is 
usually  distinct  in  the  metatergum,  especially  in  that  of  Coleoptera, 
and  is  much  less  subject  to  striking  modifications  in  contour,  etc., 
than  the  two  preceding.  Thus,  it  clearly  defines  the  postscutellum, 
as  in  figure  20. 

Transverse  divisions. — The  writer's  interpretations  of  the  modifi- 
cations and  position  of  the  four  transverse  divisions  as  represented 
in  Dendroctonus  are  demonstrated  in  figure  20. 

Prescutum  (fig.  20). — The  area  designated  as  the  prescutum  is  that 
involving  the  attachments  of  the  principal  sternotergal  muscles  and 
the  anterior  lateral  process  for  the  attachment  and  articulation  of 
the  scapular  plate.  The  anterior  limit  is  defined  by  the  prephragma, 
its  posterior  limits  by  the  anterior  suture  and  apodeme  and  the 
posterior  limit  of  the  prescutal  lobes,  and  laterally  by  the  anterior 
angle  or  limit  of  the  lateral  emargination.  The  most  important 
features  are  the  prominent  prescutal  lobes  and  anterior  lobes  for  the 
attachment  of  the  depressor  muscles,  the  prescutal  disk  for  the  small 
muscle  connecting  it  with  the  pleural  clavicula,  and  the  triangular 
prescutal  process  for  the  attachment  and  articulation  of  the  scapular 
plate.  (See,  also,  figure  21  for  the  ento tergal  characters  and  anterior 
apodeme.) 

Prephragma,  (fig.  20,  B). — The  prephragma  is  the  median  section  of 
the  anterior  vertical  area  of  the  prescutum.  Its  dorsal  and  lateral 
limits  are  defined  by  the  line  of  attachment  of  the  intersegmental 
membrane.  The  lateral  arms  in  conjunction  with  the  anterior  process 
of  the  anterior  lobe  of  the  presternum  are  greatly  extended  ventrally. 

Scutum. — The  scutum  is  represented  by  the  large  scutal  lobes  situ- 
ated each  side  of  the  scutellar  groove.  These  lobes  are  for  the  ante- 
rior attachment  of  the  large  scutal  muscles  with  the  posterior  attach- 
ment to  the  lateral  arms  of  the  postphragma.  The  lateral  margin  of 
the  scutum  is  defined  by  the  lateral  emargination  and  elevated 
scutellar  ridge  which  terminates  in  the  scutellar  process,  and  poste- 


THE   GENUS   DENDROCTONUS. 


33 


riorly  by  the  oblique  sinuated  line  of  the  median  suture  and  the 
lateral  section  of  the  posterior  ridge. 

Scutellum. — The  scutellum  is  represented  externally  by  the  area 
posterior  to  the  oblique  line  of  th$  median  suture  and  by  the  sublat- 
eral  and  lateral  ridge  which  terminates  in  the  scutellar  process,  as  is 
indicated  by  the  character  of  the  entotergum  arid  by  comparison 
with  the  less  modified  scutellar  division  in  other  insects.  The 
median  longitudinal  groove  appears  to  represent  the  median  produced 
section  of  the  scutellum  rather  than  a  part  of  the  scutum  or  prescu- 
tum,  as  indicated  by  the  character  of  the  entotergum  and  the  widely- 
separated  apodemes  of  the  median  suture  which  extend  to  and  join 


Anterior  apodeme 
''   \  k       jPrcphragwa 


Membranous  area 
^Anterior  lobe 


,.  Prcscutal  lobe- 
.Prcscntal  process 


Lateral  emargination 

ar  process 
Sen  fat  lobe 
>"Median  apodeme 

PcstscuteUar  process 


•LQU  etapleural  hook. 


ScutcllutnF 


Poslplirngma 


FIG.  2l.—Dendroctonus  valens:  Metatergum,  inner  aspect,  a,  Lateral  arm  of  prephragma;  6,  dorsal 
band;  c,  scapular  articulation;  d,  posterior  angle  of  prescutum;  e,  posterior  arm  of  postphragma;  /,  pos- 
terior apodeme;  g,  anterior  disk;  h,  posterior  margin  of  scutellum;  x,  ventral  wall  of  postscutellum. 
(Original.) 

with  the  anterior  apodeme  (fig.  21),  thus  defining  a  large  median 
triangular  area  which  is  evidently  scutellar. 

Postscutellum. — The  postscutellum  is  the  exposed  dorsal  and  lateral 
area  between  the  clearly  defined  posterior  suture  and  the  line  of 
attachment  of  the  first  abdominal  tergite.  It  is  firmly  connected 
with  the  scutellum  toward  each  side  at  a  point  near  the  base  of  the 
oblique  apodeme  of  the  middle  suture,  otherwise  the  connection  is 
membranous.  The  anterior  angles  support  the  metapleural  hooks 
(fig.  20,  EjU), which  fit  into  a  fold  in  the  dorsal  margin  of  the  postepi- 
merum  (fig.  20,  p). 

Postphragma. — The  postphragma  is  an  invagination  of  the  pos- 
terior section  of  the  postscutellum  and,  with  the  produced  posterior 
disks  and  arms,  serves  as  important  posterior  attachments  for  the 
longitudinal,  tergal,  and  oblique  scutal  muscles. 


34  THE  SCOLYTID  BEETLES. 


METAPLEURA. 


The  metapleurum  is  well  developed  and  distinctly  represented  by 
the  two  longitudinal  sclerites,  episternum  and  epimerum  (figs.  3, 
20),  with  their  anterior  dorsal  angles  greatly  produced  to  form  the 
pleural  clavicula  with  its  clavicle  and  coracoidal  processes. 

Pleural  suture  and  apodeme. — The  pleural  suture  marks  the  line  of 
division  between  the  episternum  and  epimerum,  and  extends  from  the 
dorsal  angle  of  the  coxse  to  the  apex  of  the  pleural  clavicula  and 
between  the  clavicle  and  coracoidal  process.  That  this  is  the  true 
pleural  suture  is  indicated  by  the  corresponding  prominent  pleural 
apodeme.  It  is  also  quite  evident  that  the  episternum  corresponds 
to  the  hypopleurites  and  the  epimerum  to  the  epipleurites  of  the 
abdominal  segments  (figs.  3,  22). 

Episternum. — The  episternum  is  exposed  when  the  elytra  are 
closed  (fig.  2).  The  suture  between  it  and  the  sternum  is  distinct 
and  nearly  straight,  with  the  anterior  end  curved  toward  the  coxa. 
The  posterior  ventral  angle  is  oblique  and  joins  the  posterior  dorsal 
angle  of  the  sternum;  from  here  the  posterior  margin  is  oblique  to 
its  acute  junction  with  the  epimerum  and  the  dorsal  angle  of  the 
coxal  cavity.  From  here  the  dorsal  margin  is  acutely  elevated  to 
fit  into  the  anterior  lateral  groove  of  the  elytron,  and  is  nearly  parallel 
with  the  ventral  margin  to  the  preepisternum. 

Preepisternum. — The  preepisternum  appears  to  be  represented  by 
the  narrow  declivous  anterior  section  of  the  episternum  connected 
with  the  anterior  basal  area  of  the  pleural  clavicula  and  is  apparently 
involved  in  the  formation  of  the  clavicle  process.  The  clavicle  disk 
evidently  represents  one  or  both  of  the  paraptera  of  certain  other 
insects  and  belongs  to  the  prepleura.  It  is  situated  immediately 
anterior  to  the  preepisternum.  It  is  large,  prominent,  and  partially 
exposed,  and  is  connected  by  a  chitinous  tendon  to  the  side  of  the 
clavicle  process.  This  disk  supports  the  set  of  large  clavicular  or 
sterno-pleural  muscles,  the  opposite  ends  of  which  are  attached  to  the 
sternum  and  sternellum. 

Epimerum. — The  epimerum  is  situated  between  the  pleural  suture 
and  the  tergum.  With  the  exception  of  the  extreme  posterior  ven- 
tral angle  of  the  postepimerum  it  is  covered  by  the  elytra.  The 
anterior  dorsal  angle  is  strongly  produced  to  form  the  coracoid  pro- 
cess. The  ventral  area  is  chitinous  and  is  joined  to  the  episternum 
by  the  pleural  suture,  while  the  dorsal  area  is  submembranous  tc 
membranous  to  its  junction  with  the  base  of  the  wing  membrane. 

Postepimerum. — The  posterior  ventral  angle  and  posterior  lateral 
section  represent  the  postepimerum,  as  is  indicated  by  its  articula- 
tory  junction  with  the  poststernellum  (fig.  20,  p).  The  posterior 


THE   GENUS   DENDROCTONUS. 


35 


ventral  angle  or  ventral  section  of  the  postepimerum,  which  might 
be  mistaken  for  a  postepisternum,  is  indicated  by  the  pleural  apodeme 
and  pleural  suture  wrhich  here  join  the  dorsal  angle  of  the  coxa.  It 
is  not  impossible,  however,  that  this  plate  may  represent  a  combined 
postepisternum  and  postepimerum. 

METASTERNA. 

.e  metasterna  (figs.  2,  3)  form  a  broad  rectangular  plate  separated 
to  two  lateral  sections  by  a  median  longitudinal  line.     The  pre- 
sternum  and  poststernellum  are  not  represented  by  external  parts. 


,-Spiracle  I 
-Epipleuritel 


~  Epipleurite  2 
-  -SpiracleS 
-  Epipleurite  3 


-Epipleurite  4 

-J~*Spirack  5 
•Epipleurite  5 

©-/--  Spiracle  Q 
~  'Epipleurite  6 


''^Spiracle  7 
^Epipleurite  7 


Pygidium 


'Stridulating  scraper 


FIG.  22.—Dendroctonus  valens:  Abdominal  tergites.    a,  Anterior  arm  of  epipleurite  7;  6,  posterior  arm  of 
epipleurite  7;  c,  membranous  lobes.    (Original.) 

Sternum. — The  sternum  is  evidently  represented  by  the  large  con- 
tinuous area  between  the  mesocoxse  and  the  small  median  plate  and 
the  slightly  acclivous  area  anterior  to  the  metacoxa. 

Sternellum. — The  sternellum  is  evidently  represented  by  the  pos- 
terior median  plate  and  the  posterior  acclivous  areas  (fig.  2,  a).  The 
relation  of  the  latter  to  the  sterneilar  area  is  indicated  by  the  attach- 
ment of  the  posterior  pair  of  clavicular  muscles. 


THE    ABDOMEN. 


The  abdominal  terga,  pleura,  and  sterna,  and  their  relative  pro- 
portions, are  shown  in  figures  1-3  and  22-25. 

79980—09 4 


36 


THE  SCOLYTID  BEETLES. 
ABDOMINAL  TERGITES. 


The  eight  abdominal  tergites  are  normally  covered  by  the  elytra. 
The  apparent  difference  in  the  relative  proportions,  as  indicated  by 
figures  3  and  22,  is  due  to  the  flexible  intersegmental  membrane  and 
the  fact  that  figure  20  is  from  a  balsam  mount.  The  integument 
of  1  to  6,  inclusive,  is  more  or  less  membranous,  while  that  of  7  and  8, 
with  the  exception  of  the  finely  sulcate  membranous  lobes  of  7,  is 
chitinous.  In  the  female,  8  is  covered  by  7,  and  forms  the  so-called 


FIG. 23.— Dendroctonus  valens:  Male, abdominal  tergites 7 and 8.  A,  Tergite  8  (pygidium),  ventral;  JB,same, 
dorsal;  C,  same,  ventral,  showing  position  of  sternite  8;  D,  tergite  7  (propygidium),  dorsal;  E,  same, 
ventral;  a,  anterior  arm  of  epipleurite  7;  6,  posterior  arm  of  epipleurite  7;  c,  membranous  lobe;  d, 
epipleural  process;  e,  hypopleural  arm  of  sternite  8;  /,  pleural  opening;  g,  anal  space;  h,  ventral  fold;  i, 
rudimentary  spiracle  8;  j,  epipleural  disk;  k,  apical  spine;  I,  stridulating  process;  m,  sensory  bristles; 
n,  enlarged  section  of  lateral  area;  o,  enlarged  section  of  membranous  lobe;  p,  stridulating  scraper. 
(Original.) 

"pygidium,"  while  in  the  male  8  is  distinct  and  together  with  7  forms 
the  so-called  "divided  pygidium." 

Pygal  tergites  of  the  male. — The  pygal  tergites  of  the  male  are  shown 
in  figure  23,  A,  B,  C,  D,  E.  Tergite  7  is  the  propygidium  and  as  a 
bearer  of  generic  and  sexual  characters  is  the  most  important  of  the 
entire  series.  In  the  male  the  posterior  margins  between  the  epi- 
pleurites  converge  toward  the  apex,  which  is  produced  into  a  bifid 
process  and  supports  the  stridulating  scrapers.  The  posterior  area 
of  the  tergite  is  thickened  and  strengthened  to  meet  the  requirements 
of  stridulation.  There  is  a  broad  ventral  fold  (fig.  23  E,  7i)  of  the 
integument  which  may  serve  a  similar  function  to  that  of  a  sounding 
board. 


THE   GENUS  DENDROCTONUS. 


37 


The  median  area  is  triangular  in  form  and  covered  with  bristles 
and  hairs  rising  from  variously  formed  bases.  On  its  face  and  some- 
times on  the  posterior  area  there  are  a  few  irregularly  arranged 
truncate  tubercles  (Z),  m),  each  bearing  a  short,  stiff  bristle.  These 
may  possibly  function  as  sense  organs. 

The  membranous  lobes  are  subovate,  finely  sulcate,  and  thickly 
clothed  with  reclining  microscopic  spines  (o).  The  exact  function 
of  these  lobes  is  not  known  to  the  writer.  Tergites  4,  5,  and  6  have 
similar  lobes.  The  other  dorsal  and  ventral  characters  are  made 
sufficiently  clear  in  D  and  E. 


FIG.  24,—Dendroctonus  valens:  Female,  abdominal  tergites  7  and  8.  c,  Anterior  arm  of  epipleurite  7; 
6,  membranous  area  surrounding  spiracle;  c,  membranous  lobe;  d,  epipleural  process;  e,  hypopleural 
process  of  steraite  8;  /,  pleural  opening;  g,  anal  space;  h,  ventral  fold;  i,  rudimentary  spiracle;  j,  epipleural 
disk;  k,  median  membranous  connection  of  the  lateral  sections  of  sternite  8.  (Original.) 

Tergite  8  (A,  B)  is  the  pygidium.  This,  in  the  male,  is  always 
larger  and  more  exposed  beyond  the  margin  of  tergite  7  than  in  the 
female.  The  relative  proportions,  as  compared  with  7,  and  the  dorsal 
and  ventral  characters  are  clearly  shown  in  A  and  B.  The  lateral 
arms  serve  as  attachments  for  pleural  muscles  and  articulating  mem- 
brane and  ligaments.  In  C  the  abdominal  sternite  is  added  to  show 
its  relative  position  and  proportions. 

Py gal  tergites  of  the  female. — The  pygal  tergites  of  the  female  are 
shown  in  figure  24,  A,  B,  C,  D,  E,  F. 

Tergite  7  (propygidium)  is  much  more  simple  in  structural  details 
in  the  female  than  in  the  male,  and  tergite  8  (pygidium)  is  also  more 
simple  and  shorter,  being  almost  or  entirely  covered  by  7  when  in 
normal  position. 

The  characters  of  sternite  8  are  shown  in  Dt  the  most  important 
of  which  is  the  median  membranous  area. 


38 


THE    SCOLYTID   BEETLES. 


ABDOMINAL  PLEURITES. 


At  the  lateral  ends  of  the  abdominal  tergites  and  sternites  there 
are  well-defined  areas  (figs.  3,  22,  25),  which  may  be  designated  as 
pleurites.  Those  situated  immediately  above  the  pleural  suture  and 
bearing  the  spiracles  may  be  referred  to  as  epipleurites,  while  those 
of  the  sternites  which  are  immediately  below  the  pleural  suture  may 
be  designated  as  hypopleurites;  both  series  are  well  defined  in 
Dendroctonus. 

In  a  lateral  view  (fig.  3)  seven  epipleurites  and  five  hypopleurites 
are  clearly  defined,  with  the  eighth  epipleurite  and  the  second  hypo- 
pleurite  indicated,  and  when  the  abdomen  is  removed  both  the  first 
and  second  of  the  latter  series  are  quite  distinct. 


Ilypopleurites . ^ 


Coxal  cavitu 


Inlercoxal  process 


FIG.  25.— Dendroctonus  valens:  Abdominal  sternites,  ventral  and  lateral  aspects.  A ,  Lateral;  B,  ventral; 
a,  sternite  1 ,  faintly  indicated;  6,  sternite  g,  faintly  indicated.    (Original.) 

ABDOMINAL  STERNITES. 

The  characters  of  the  abdominal  sternites  are  shown  in  figures  2, 
3,  and  25.  There  are  eight,  corresponding  to  the  eight  tergites,  but 
only  five  are  exposed,  viz,  3  to  7,  which  are  densely  chitinized  and 
clearly  defined  by  four  sutures. 

Sternites  1  and  2  and  the  anterior  portion  of  3  are  covered  and 
obscured  by  the  large  metacoxa  and  form  the  posterior  wall  of  the 
coxal  cavity.  They  are  fused,  but  the  sutures  are  indicated  by  faint 
lines.  Sternite  3  (first  ventral  segment  of  some  writers)  has  the 
median  area  produced  anteriorly,  and  with  faintly  indicated  median 
portions  of  sternites  2  and  1  it  forms  the  intercoxal  process,  the  apex 
of  which  forms  a  junction  with  the  metasternellar  piece.  The 
anterior  exposed  margin  forms  the  posterior  margin  of  the  coxal 
cavity,  but  the  junction  with  the  preceding  segment  is  but  faintly 


THE   GENUS   DENDROCTONUS.  39 

indicated  in  the  wall  of  the  coxal  cavity.  Sternites  4,  5,  and  6  are 
nearly  of  equal  length,  while  sternite  7  is  nearly  as  long  as  5  and  6 
together,  with  the  posterior  margin  broadly  curved  and  forming 
the  apex  of  the  exposed  series.  Sternite  8  (figs.  23,  C,  and  24,  D)  is 
entirely  covered  by  7,  and  is  represented  in  the  male  by  a  narrow 
chitinous  rim  below  the  anal  opening,  while  in  the  female  the  median 
section  of  this  sternite  is  membranous. 

Suture  3,  between  sternites  3  and  4,  is  the  first  visible  suture,  and 
is  rigid  and  straight  throughout,  while  sutures  4,  5,  and  6  are  slightly 
flexible  and  are  strongly  recurved  toward  and  between  the  hypo- 
pleurites,  thus  presenting  an  important  generic  character. 

SPIRACLES. 

There  are  9  well-developed  spiracles,  2  thoracic  and  7  abdominal, 
with  the  rudiments  of  a  tenth.  The  large  mesothoracic  spiracle  is 
located  in  the  intersegmental  membrane  between  the  prothorax  and 
mesothorax,  and  lies  between  the  preepisternal  process  and  the 
anterior  ventral  angle  of  the  preepisternum.  It  overlaps  the  anterior 
margin  of  the  latter  for  half  its  length,  but  is  completely  covered  and 
obscured  by  the  epimeral  area  of  the  prothorax.  The  metathoracic 
spiracle  is  situated  in  the  intersegmental  membrane  between  the 
metathorax  and  mesothorax,  and  concealed  beneath  the  dorsal 
margin  of  the  mesepimerum.  The  abdominal  spiracles  1-7  are  con- 
spicuous; 1  is  very  large  and  situated  in  the  epipleurite  just  posterior 
to  the  pleural  hook  of  the  metapostscutellum;  2-7  are  situated  in 
their  respective  epipleurites,  as  shown  in  figures  3,  22,  23,  and  24,  while 
8  is  evident,  but  rudimentary. 

THE    LEGS. 

The  structures  and  characters  of  the  parts  of  the  legs  are  so  well 
illustrated  in  the  figures  (figs.  3,  26-29)  that  they  do  not  require 
detailed  description.  The  procoxae  and  mesocoxae  are  large,  globose, 
and  prominent,  the  former  subcoritiguous  and  the  latter  widely 
separated  by  the  elevated  intercoxal  or  sternellar  piece,  while  the 
metacoxae  are  oblong,  oval,  and  separated  by  the  process  of  the 
third  abdominal  sternite.  There  is  no  striking  difference  in  the 
anterior,  middle,  and  posterior  trochanters,  femora,  tibiae,  and 
tarsi.  The  trochanters  are  small;  the  femora  are  moderately  stout, 
and  each  is  as  long  as  its  tibia,  which  is  dilated  toward  the  apex  and 
armed  on  its  outer  lateral  margin  with  stout  teeth.  The  anterior 
dorsal  area  has  a  distinct  tarsal  groove  for  the  retractile  tarsus,  as 
shown  in  figures  26  to  29.  The  tarsi  are  each  more  than  half  as  long 
as  their  tibiae,  and  have  five  joints;  joint  1  is  always  longer  than  2, 
but  never  as  long  as  2  and  3  together;  3  is  distinctly  bilobed,  the 


40 


THE   SCOLYTID   BEETLES. 


lobes  slightly  longer  than  joint  4;  joint  5  from  tip  of  lobes  of  3  is 
never  as  long  as  the  others  (1  to  3)  together,  but  sometimes  shorter 
than  1  and  rarely  equal  to  2  and  3.  In  the  males  this  joint  is  often 
longer  than  in  the  female. 

The  trochlear  articulation  of  the  tibia  with  the  tarsus  is  shown  in 

figure  26,  in  which  the 
other  more  import  ant  char- 
acters are  shown  and 
named. 

THE    WINGS. 


Notwithstanding  the  vast 
amount  of  published  data 
on  the  wings  of  insects,  there 
is  yet  much  difference  of 
opinion  among  the  leading 
authors  in  regard  to  some 
of  the  details,  and  much 
confusion  exists,  due  to 
different  interpretations  of 
the  homologies  of  the  ele- 
ments of  the  wing  and  its 
articulatory  accessories.  A 
detailed  investigation  has 
been  made  of  the  basal 
areas  of  the  wings  of  rep- 
resent  atives  of  different 
orders  of  insects,  to  deter- 
mine facts  relating  to  the 
fundamental  plan  of  devel- 
opment and  modification, 
and  the  system  of  orgaiii- 
zation  of  the  elements  as 
represented  in  Dendroc- 
tonus. 

Nomenclature. — W  h  i  1  e 


FIG.  2Q.—Dendroctonus  valens:  Tibia  and  tarsus,  articulation, 
etc.  A, 4-44.  tibia,  ventral  view;  B,  teff  tibia,  dorsal  view; 
femora,  ental  view;  D,  iatftibia,  dextral  view  of  base; 
E,  tdft  tibia,  sinistral  view  of  base;  F,  tarsus;  a,  apical  tooth; 
6,  subapical  tooth;  c,  tarsal  groove;  d,  subapical  ridge;  e, 
marginal  teeth;  /,  ciuii'ti^4  margin;  g,  deKtooi  margin;  h, 
median  fossa;  i,  lateral  condyle  of  tibia;  j,  anterior  fossa;  k, 
lateral condyj»<rffemur;  I,  lateral  fossa  of  femur;  m,  median 
condyle  pffemur;  n,  attachment  of  extensor  muscle;  o,  basal 
foramen;  p,  attachment  of  flexor  muscle;  q,  basal  groove;  r, 
tibial  groove.  (Original.)  ,  .  a.  /A 


the  more  generally  accepted  nomenclature  has  been  adopted,  it  has 
seemed  necessary  to  revise  and  more  definitely  define  the  application 
of  some  of  the  old  names  and  to  introduce  some  new  ones  to  desig- 
nate the  elements  heretofore  obscurely  defined. 

Attachments  and  articulations. — There  are  certain  elements  in  the 
structure,  mechanism,  attachments,  and  articulation  common  to 
the  wings  of  all  insects,  but  within  defined  limits  and  according  to  a 
definite  system  modifications,  additions,  and  reductions  occur. 
Therefore  the  presence  or  absence  of  a  given  element  should  be 
detected  in  any  form  of  wing. 


THE   GENUS   DENDROCTONUS. 


41 


Primary  elements  of  the  Dendroctonus  wing. — The  primary  wing 
elements  and  their  relations  to  each  other  as  represented  in  Den- 
droctonus may  be  summarized  as  follows:  The  structure  consists  of  a 
dorsal  and  ventral  membrane  or  cliitinous  integument.  The  primary 
tracheae  are  costal,  subcostal,  radial,  cubital,  and  anal.  The  primary 
veins  are  costa,  subcosta,  radius,  media,  cubitus,  and  anal.  The 
wing  plates  are  scapular,  subscapular,  flexor,  subflexor,  radial,  and 
medial.  The  wings  are  attached  by  membrane  to  the  tergum  and 


7  8  9  t$. 

VENTRAL 

Fi<;.  27.— Dendroctonus:  fesffc-tibise,  dorsal  and  ventral  aspects.  /,  brevicomis;  2,  barberi;  3,  convexifrons, 
4,frontalis;  5,  arizonicus;  6,  mexicanus;  7,  parallelocollis;  8,  approximatus;  9',  monticolx;  10,  ponderosse. 
(Original.) 

pleurum,  and  by  ligaments  and  tendons  to  tergal  and  pleura!  proc- 
esses and  muscle  disks.  The  pleural  processes  are  the  clavicle  and 
coracoid  processes,  which  together  form  the  pleural  clavicula.  The 
tergal  processes  are  the  prescutal,  scutellar,  and  postscutellar. 

Elements  of  wing  motion. — The  elements  of  wing  motion  are  the 
clavicular  disk  and  clavicular  muscle,  pleural  disk  and  pleural  muscle, 
flexor  and  flexor  muscles,  prescutal  disk  and  muscles,  anterior  pres- 
cutal lobe  and  anterior  sternotergal  muscles,  posterior  prescutal  lobe 
and  posterior  sternotergal  muscles,  scutal  lobe  and  scutal  muscles, 


42 


THE    SCOLYTID   BEETLES. 


scutellar  lobe,  postscutellar  processes,  prephragma,  and  postphragma ; 
also  the  pleural  clavicula,  clavicle,  coracoidal,  tergal,  prescutal,  scu- 
tellar, and  postscutellar  processes,  and  connecting  ligaments. 

MESOTHORACIC  AND  METATHORACIC  WINGS. 

While  there  is  a  wide  difference  in  the  appearance  and  structural 
details  of  the  elytra  and  the  hind  wings  of  beetles,  they  are  evidently 
homologous  and  differ  only  in  their  modification  in  structure  and 
function. 


VENTRAL 

FIG.  28.—Dendroctonus:  beftrtibiae,  dorsal  and  ventral  aspects.    12,  simplex;  13,  pseudotsugse;  14,  piceaperda; 
15,  engelmanni;  16,  borealis;  17,  obesus;  18,  ruflpennis.    (Original.) 

Structure. — The  wing  consists  of  two  layers  of  integument,  the  dor- 
sal evidently  rising  from  the  tergites  and  the  ventral  from  the  epi- 
pleurum  (epimerum).  Between  these  layers  there  is  a  system  of  tra- 
cheation  and  circulation.  The  integument  of  the  meso thoracic  wing 
or  elytron  is  chitinous  throughout,  while  that  of  the  metathoracic 
or  hind  wing,  with  the  exception  of  the  veins  and  basal  pieces,  is 
membranous. 

Tracheation. — The  same  system  of  primary  tracheae  prevails  in 
both  the  elytra  and  the  hind  wings.  In  the  former  it  corresponds  in 


THE   GENUS   DENDROCTONUS. 


43 


general  position  to  that  of  the  primary  veins  in  the  latter,  thus  con- 
forming to  the  prevailing  system  in  fully  developed  wings  of  all 
insects.  The  primary  tracheae  are  costal,  subcostal,  radial,  medial, 
cubital,  and  anal.  In  the  elytron  these  occupy  the  marginal  and 
alternating  interspaces  between  the  longitudinal  striaB  or  rows  of 


tibiae,  dorsal  and  ventral  aspects.    20,  punctatus;  21,  micans;  22a,  22b, 
terebrans;  23,  valens.    (Original.) 

mctures,  while  in  the  hind  wing  they  follow  approximately  the 
primary  veins. 

METATHORACIC  OR  HIND  WINGS. 

The  hind  or  metathoracic  wings  (figs.  1,  20,  and  30)  are  a  third 
longer  than  the  elytra  or  mesothoracic  wings,  under  which  they  are 
folded  when  at  rest.  In  consequence  the  veins  toward  the  middle 
of  the  wings  are  flexible  and  adapted  to  the  requirements  of  folding 
and  unfolding. 


44 


THE   SCOLYTID   BEETLES. 


Basal  area  (fig.  30). — The  basal  area  is  that  in  which  the  basal 
plates  and  head  of  the  veins  occur.  In  this  area  there  are  four 
axillary  plates,  which  are  more  or  less  common  to  insect  wings  in 
general.  These  appear  to  belong  to  the  wing  rather  than  to  the 
body  structures,  and  are  here  designated  as  scapular,  subscapular, 
flexor,  radial,  and  medial  plates.  They  are  discussed  in  greater 
detail  under  wing  articulation. 

Veins. — The  six  primary  veins  represented  in  the  hind  wing  are 
costa,  subcosta,  radius  1  and  2,  media  1  and  2,  cubitus  1  and  2,  and 
anal,  which  last  is  rudimentary. 


—  Sc 


--7? 


-Cu 


FIG.  3Q.—Dendroctonus  valens:  Diagram  of  basal  area  of  hind  wing,  a,  Scapular  plate;  ft,  subscapular 
plate;  c,  flexor  plate;  d,  radial  plate;  e,  medial  plate;  /,  tendon  attachment;  g,  articulation;  h,  subcostal 
head;  i,  costal  head;./,  costal  tongue;  k,  radial  head:  I,  medial  head;  m,  cubital  head;  n,  anal  head; 
o,  scapular  condyle;  p,  scapular  arm;  q,  scapular  base;  r,  articulatory  margin;  s,  connection  of  costa 
with  subcosta;  t,  flexor  arm;  u,  connection  of  medial  plate  with  flexor;  C,  costa;  Sc,  subcosta;  E,  radius; 
M, media;  Cu,  1, 2,  cubitus  1  and  2;  A ,  anal.  (Original.) 

Costa. — In  Dendroctonus  and  most  beetles  the  vein  which  corre- 
sponds to  the  costal  trachea  is  confined  to  the  basal  area,  and  forms 
the  anterior  basal  angle.  The  head  is  produced  beyond  the  head  of 
the  subcosta,  with  which  it  is  fused  to  form  the  articulating  fossa. 
The  produced  head  of  this  vein  appears  to  function  as  an  important 
accessory  of  the  clavicle  muscles  in  extending  and  depressing  the 
wing,  since  it  is  connected  with  the  clavicle  condyle  and  clavicle  disk 
by  tendons.  The  vein  proper  extends  outward  but  a  short  distance 
to  its  submembranous  connection  with  the  subcosta,  and  from  that 
point  the  costal  margin  is  occupied  by  it  and  the  subcosta  to  its 


THE   GENUS  DENDROCTONUS. 


45 


junction  with  the  radius,  which  appears  to  form  the  broad  chitinous 
costal  area  to  near  the  apex,  with  branch  2  as  a  distinct  vein. 

Subcosta. — The  subcosta  is  the  principal  vein  of  the  wing.     It  gives 
rigidity  to  the  base,  and  with  the  head  of  the  costa  forms  the  articu- 


3235; 


*  s.  s. 


lating  head.     It  is  broadest  where  it  is  joined  by  the  costa,  and  is 
strongly  narrowed  to  its  junction  with  the  radius. 

Radius. — The  radius  is  an  important  vein  in  giving  additional  rigid- 
ity to  the  median,  distal,  and  costal  areas  and  in  forming  the  folding 


46 


THE   SCOLYTID   BEETLES. 


hinge.     It  arises  through  the  radial  plate  from  the  subscapula,  and 
joins  and  fuses  with  the  head  and  posterior  edge  of  the  subcosta  to 


FIG.  32.—Dendroctonus  valens:  Basal  process  of  right  elytron.  A,  Ventral;  B,  latero-sinistral;  C,  dorsal; 
D,  latero-dextral;  c,  foramen  of  articulatory  head;  b,  subcostal  head;  c,  costal  head;  d,  costal  fold;  e, 
costal  margin;  /,  callus;  g,  basal  foramen;  h,  anal  fold;  i,  muscle  disk;  j,  radial  plate;  k,  posterior  ven- 
tral area;  Z,  anal  margin;  ra,  posterior  dorsal  area;  Sc,  subcostal  area.  (Original.) 


Stria' 

I 


FIG.  33,—Dendroctonus  valens:  Declivital  section  of  elytra,  a,  Ventral  shoulder;  b,  dorsal  shoulder;  c, 
sutural  tongue;  d,  ventral  lip;  e,  dorsal  lip;/,  sutural  groove;  g,  rugose  surface  of  apical  wing-lock;  h, 
stridulating  rasp;  i,  apical  wing-lock;  j,  suture;  A,  anal  canal;  Cu,  cubital  canal;  M,  medial  canal;  R 
radial  canal;  Sc,  subcostal  canal;  C,  costal  canal;  D,  transverse  section;  E,  ventral  aspect;  F,  trans- 
verse section  through  stridulating  rasp;  G,  right  elytron;  H ,  left  elytron.  (Original.) 

the  point  where  it  becomes  broadened  and  obliquely  rugose.  Here 
it  separates  from  the  subcosta  and  joins  the  media  by  a  short  cross- 
vein,  and  thence  proceeds,  as  shown  in  the  figure. 


TIIK   CKNTS   DENDROCTONUS. 


47 


10    9 


7     G    5    4 


3    2 


^ 
Interspaces 

-T  rackets 


M«lia. — The  media  is  distinctly  connected  with  a  basal,  irregular, 
flexible  medial  plate,  which  is  joined  to  the  flexor,  radial,  and  sub- 
scapular  plates  by  membrane  and  flexible  chitin.  Near  the  distal 
limit  of  the  basal  area  there  is  an  evident  fold  or  cross  vein  connecting 
the  base  of  the  media  with  the  base  of  the  cubitus,  from  which  it 
proceeds  outward" to  the  hinge,  and 
from  this  point  two  branches  ex- 
tend to  the  anal  margin. 

Cubitus. — The  cubitus  rises  from 
the  outer  border  of  the  basal  area 
and  apex  of  the  flexor  and  has  two 
branches.  Branch  1  extends  to  the 
margin.  Branch  2  is  short  and 
more  or  less  rudimentary. 

Anal. — The  anal  vein  is  evidently 
represented  by  the  broad,  short  spur 
arising  from  the  base  of  the  cubitus, 
and  does  not  extend  to  the  margin. 

Wing  attachment. — The  wing  is 
attached  to  the  body  by  chitinous 
dorsal  and  ventral  integument,  the 
latter  arising  from  the  dorsal  mar- 
gin of  the  epimerum,  and  the  for- 
mer from  the  lateral  margins  of  the 
prescutum,  scutum,  and  scutellum, 
as  indicated  in  the  pupa.  The  heads 
or  roots  of  the  veins  are  attached 
by  a  system  of  connecting  chitinous 
tendons  and  ligaments  to  the  pleural 
and  tergal  processes  and  disks. 

Wing  articulation. — The  principal 
articulation  of  the  wing  is  between 
the  wing  head  formed  by  the  costa 
and  subcosta  and  the  condyles  of 
the  clavicle  and  coracoid  processes 
together  with  the  scapular  plate.  The  scapular  plate  is  also  con- 
nected with  the  prescutal  process  by  articulating  membrane  and 
ligaments. 

Pleural  clavicula  ("clavicula  thoracique,"  Chabrier,  1820). — The 
position  and  function  of  the  articular  processes  of  the  episternum 
and  epimerum  (fig.  20,  pc),  as  represented  more  or  less  distinctly  in  all 
insects,  are  in  Dendroctonus  so  strikingly  analogous  with  that  of  the 
clavicle  and  coracoid  in  winged  vertebrates  as  to  suggest  to  the  writer 
the  same  names.  The  giving  of  these  names  conforms  with  the  prac- 
tice of  adopting  for  insect  anatomy  such  of  the  nomenclature  of  ver- 


FIG.  34.— Dendroctonus  valens:  Diagram  of  ely- 
tron, showing  striae,  interspaces,  and  tracheae. 
Striae  1-10;  interspaces  1-11.  Tracheae:  £,  cos- 
tal; Sc,  subcostal;  R,  radial;  M,  medial;  Cu, 
cubital;  A,  anal.  (Original.) 


48  THE   SCOLYTID   BEETLES. 

tebrate  anatomy  as  is  applicable  to  parts  in  insects  having  the  same 
or  similar  functions.  Subsequently  the  writer's  attention  was  called 
to  the  fact  that  the  same  idea  was  suggested  to  Chabrier. 

In  Dendroctonus  the  clavicle  and  coracoid  processes  are  prominent 
and  clearly  defined,  the  condyle  of  the  former  being  definitely  con- 
nected with  that  of  the  head  of  the  subcostal  vein,  which  articulates 
between  the  condyles  of  the  clavicle  process  and  scapular  plate. 
Chabrier's  name  clavicula  has  been  adopted  for  the  combined  clavicle 
and  coracoid  processes. 

Tergal  processes  (fig.  20). — The  processes  of  the  tergal  area,  which 
have  more  or  less  important  functions  as  articulatory  accessories, 
may  be  designated  as  prescutal,  scutellar,  and  postscutellar. 

Presented  process. — The  prescutal  process  is  represented  by  a  tri- 
angular extension  of  the  posterior  angle  of  the  prescutum,  and  is  of 
primary  importance  as  an  accessory  to  the  scapular  plate. 

Scutellar  process. — The  scutellar  process  is  represented  by  the  thick- 
ened lateral  margin  of  the  lateral  impression  and  by  the  produced, 
acute,  anterior  angle.  It  is  attached  along  its  lateral  margin  to  a 
pleural  tendon  connecting  the  pleural  disk  to  the  flexor  and  sub- 
scapula.  This  process  is  also  accessory  to  the  flexor. 

Postscutellar  process. — The  postscutellar  process  is  an  extension  or 
arm  of  the  anterior  angle  of  the  postscutellum,  and  has  its  apex 
attached  to  the  pleural  disk  and  to  the  pleural  hook. 

Lateral  emargination. — What  is  termed  the  lateral  emargination 
is  the  emargination  in  the  side  of  the  scutum  between  the  posterior 
angle  of  the  prescutum  and  the  scutellar  process.  It  is  present  in 
most  of  the  insects  and  appears  to  facilitate  the  functions  of  the  flexor 
muscle. 

Lateral  impression. — The  lateral  impression  is  an  impression  to 
accommodate  the  flexor  plate  when  the  wing  is  at  rest. 

Basal  elements. — The  basal  elements  of  the  wing  which  function  as 
articulatory  accessories  are  here  referred  to  as  head  of  costal  vein, 
scapular,  subscapular,  radial,  medial,  and  flexor  plates  (fig.  30). 

Head  of  costal  vein  (i) . — The  head  of  the  costal  vein  is  produced 
beyond  its  fused  connection  with  the  head  of  the  subcosta.  It  is 
connected  to  the  head  of  the  clavicle  by  a  ligament,  and  evidently 
functions  in  extending  the  wing  forward  as  well  as  in  contributing  to 
other  motions. 

Scapular  plate  (a). — In  form  and  function  the  fundamental  basal 
plate,  which  we  here  call  scapular  plate,  is  very  suggestive  of  the 
scapula  of  vertebrates,  but  its  peculiar  functions  require  quite  differ- 
ent tergal  connections.  It  is  joined  by  ligaments  to  the  prescutal 
process  and  lateral  margin  of  the  prescutal  lobe  in  such  a  manner  as 
to  facilitate  part  of  its  functions — that  of  unfolding,  elevating,  and 
depressing  the  wing.  Its  condyle  articulates  directly  with  the 


THE   GENUS  DENDROCTONUS.  49 

dorsal  or  inner  edge  of  the  head  of  the  subcosta  and  with  the  clav- 
icle condyle. 

Subscapular  plate  (b) . — The  subscapular  plate  is  more  complicated  in 
its  structure  than  the  scapular  plate,  to  which  it  is  a  direct  accessory, 
the  two  being  closely  joined  by  articulating  ligament.  It  functions 
as  an  intermediate  patella-like  connection  of  the  system  of  tendons 
which  connect  the  pleural  disk  at  the  head  of  the  pleural  muscle  wTith 
the  flexor,  head  of  scapular  plate,  head  of  coracoidal  process,  head  of 
subcosta,  etc.  Therefore  it  must  be  of  fundamental  importance  in 
wing  motion. 

Radial  plate  (d) . — The  radial  plate  is  represented  by  a  thin  chitinous 
piece  connecting  the  radius  with  the  subscapula. 

Medial  plate  (e) . — The  medial  plate  is  of  flexible  chitin  connecting 
the  media  with  the  flexor  and  subscapula. 

Both  the  radial  plate  and  flexor  plate  evidently  function  as  articu- 
lating accessories. 

Flexor  plate  (c) . — The  flexor  plate  comes  next  to  the  scapular  plate 
in  its  fundamental  importance  in  wing  connection  and  articulation,  and 
is  especially  fitted  in  structure  and  muscular  connection  for  its  pri- 
mary function  of  flexing  and  longitudinally  folding  the  wing,  as  well 
as  in  the  reverse  action  of  contributing  to  its  outward  extension  and 
rigidity  during  flight. 

MESOTHORACIC  WINGS  OR  ELYTRA. 

The  form  and  general  structure  of  the  elytra  are  shown  in  figures  1 
id  31.  They  are  oblong,  rigid  shields,  with  a  subacute  apex  and  a 
icate  declivous  base  and  a  produced  articulating  head.  The 
structure,  like  that  of  the  metathoracic  wing,  consists  of  two  layers 
of  integument  inclosing  the  tracheal  and  circulatory  system,  but 
instead  of  the  dorsal  and  ventral  layers  being  partially  composed  of 
flexible  membrane,  they  are  chitinous  throughout.  The  ventral 
layer  is  thin  and  smooth,  while  the  dorsal  one  is  thick  and  deeply 
sculptured. 

Tracheation. — The  six  primary  tracheae  (figs.  31,  34)  occupy  the 
marginal  and  the  alternating  longitudinal  spaces  between  the  rows 
of  punctures.  Each  has  numerous  fine  lateral  branches  passing  be- 
tween the  punctures  into  the  intervening  interspaces,  producing  a 
network  of  fine  tracheae,  with  the  punctures  representing  the  mesh. 
Thus  we  have  a  probable  explanation  of  the  primary  cause  of  the 
system  of  punctures  in  the  elytra  and  the  longitudinal  and  tranverse 
thickened  spaces  between  them.  The  thickened  and  elevated  areas 
are  due  to  a  concentration  of  chitin  over  the  tracheal  and  circulatory 
canals,  while  the  punctures  and  grooves  are  the  points  of  adhesion  or 
junction  of  the  two  layers  to  form  the  walls  between  the  canals. 


50  THE  SCOLYTID  BEETLES. 

Sculpture. — The  dorsal  chitinous  layer  presents  many  and  varied 
characters  of  sculpture,  the  principal  elements  of  which  are  the 
striae,  including  the  longitudinal  impression  and  rows  of  punctures. 
The  interspaces  are  longitudinal  spaces  between  the  strise.  The 
rugosities  of  the  interspaces  and  strise  and  the  elevated  rugose  basal 
margin  are  all  characteristic  elements  of  sculpture.  There  are  ten 
strise  and  eleven  interspaces.  For  convenience  in  referring  to  the 
variable  characters,  these  are  numbered,  beginning  with  those  next  to 
the  dorsal  suture,  when  the  elytra  are  closed,  or  with  the  posterior  or 
anal  margin  when  the  elytra  are  open.  Thus  we  have  interspaces  1 
to  11,  and  strise  1  to  10  (figs.  31,  33). 

Interspaces. — In  an  ideal  system  (fig.  34)  interspaces  1  to  5  are 
continuous  toward  the  apex  with  11  to  7,  leaving  6  independent 
between  5  and  7.  The  primary  trachese  occupy  interspaces  1,  3,  5,  7, 
9,  and  11.  There  is,  however,  more  or  less  variation  and  modifica- 
tion in  the  elytra  of  beetles  from  this  ideal  arrangement  and  espe- 
cially upon  the  distal  ends  and  their  junctions  with  each  other  on 
the  declivital  area.  In  Dendroctonus  interspace  1  is  usually  more 
elevated  and  continuous  to  apex,  where  it  joins  the  very  narrow 
marginal  11;  2  is  less  elevated  to  flat,  narrowed  toward  apex,  and 
joins  the  very  narrow  and  obscure  submarginal  10,  which  becomes 
broader  and  distinct  toward  the  base;  3  joins  the  distinct  9;  4  joins 
6  around  the  apex  of  5,  and  also  joins  8  around  the  apex  of  7. 

Stride. — In  the  ideal  arrangement  (figs.  1,  31,  34),  strise  1  to  5  are 
continuous  with  strise  10  to  6,  but  the  usual  arrangement  on  the 
declivity  in  this  genus  is  1  to  3  continuous  with  10  to  8,  while  4  is 
continuous  with  5,  and  6  with  7.  The  strial  punctures  range  from 
small  to  coarse  and  from  very  distinct  to  obscure,  and  are  some- 
times variable  in  size  and  appearance  in  the  same  species.  The  pre- 
vailing condition,  however,  of  relative  obscurity  or  distinctness  in 
different  species  is  of  considerable  specific  importance.  The  strial  im- 
pressions also  vary  within  the  genus  from  scarcely  to  distinctly  or 
deeply  impressed,  and  the  prevailing  condition  within  the  species  is 
of  considerable  value.  The  elytral  declivity,  as  is  usual  in  the  scoly- 
tid  beetles,  bears  some  of  the  more  important  specific  and  second- 
ary sexual  characters. 

The  other  character-bearing  areas  of  the  elytra  are  the  lateral, 
median,  and  the  dorsal  toward  the  vertex  and  base. 

Vestiture. — The  elytra  are  more  or  less  distinctly  clothed  with 
short  or  long  hairs.  The  length,  size,  arrangement,  and  areas  occu- 
pied furnish  important  taxonomic  characters  in  distinguishing  the 
major  and  some  of  the  minor  divisions,  as  shown  in  the  synoptic 
table.  A  progressive  modification  in  vestiture  is  from  very  short 
hairs  over  the  entire  surface  to  longer  hairs  and  sparsely  arranged 


THE    GENUS   DENDROCTONUS.  51 

bristles  toward  the  vertex  of  the  declivity  and  on  the  declivity 
itself,  or  to  fine  and  coarse  long  hairs  over  the  entire  surface. 

Lateral  fold  or  costal  groove  (fig.  31,  n,  o). — In  the  costal  edge  of 
the  elytron,  from  near  the  base^o  the  median  section,  there  is  a 
lateral  or  costal  groove  for  the  reception,  when  the  elytra  is  closed, 
of  the  corresponding  produced  -and  acute  dorsal  edge  of  the  epi- 
sternujn.  There  is  also  a  deeper  and  broader  groove  in  the  median 
section  of  the  costal  area,  for  the  reception  of  the  produced  dorsal 
edges  of  hypopleurites  3  and  4.  According  to  LeConte  and  other 
writers,  this  lateral  groove  is  an  important  subordinal  character. 

Sutural  tongue  and  groove  (fig.  33,  a-f). — In  the  sutural  edge  of  the 
left  elytron  there  is  a  deep  lateral  groove  and  produced  ventral  edge 
for  the  reception  of  the  corresponding  produced  lateral  edge  or 
tongue  of  the  right  elytron,  thus  forming  a  tongue  and  groove  suture. 
Toward  the  apex  both  the  ventral  edge  of  the  left  and  the  tongue  of 
the  right  are  dilated  to  facilitate  the  locking  of  the  elytra  when  they 
are  closed. 

Stridulating  accessories. — In  the  male  there  is  a  transversely  and 
microscopically  sulcated  area  on  the  ventral  surface  toward  the 
suture  and  apex  of  each  elytron  (fig.  33).  When  the  elytra  are  closed 
this  forms  a  continuous  filelike  surface  situated  directly  above  the 
stridulating  scraper  of  the  seventh  abdominal  tergite  or  propygid- 
iiun.  A  peculiar,  independent,  upward  and  backward  motion  of 
the  propygidium  brings  the  scraper  in  contact  with  the  file,  and 
thus  produces  a  peculiar  chirping  sound  which  is  quite  audible  to  the 
human  ear. 

The  exact  location  of  the  organs  of  hearing  in  these  beetles  has 
not  been  determined. 

Basal  and  pleural  elements. — The  basal  process,  or  articulatory  arm 
(fig.  32)  of  the  elytron  appears  to  represent  the  fused  heads  of  the 
costa,  subcosta,  and  radial  veins.  The  usual  scapular,  subscapular, 
flexor,  and  medial  plates  are  quite  definitely  represented,  and  occupy 
the  same  relative  positions  as  in  the  metathoracic  wing.  The  pleural 
clavicula  are  represented  in  the  mesothorax  by  the  clavicle  and  cora- 
coidnl  processes,  which  are  fused  beneath  the  anterior  dorsal  angle 
of  the  episternum  to  form  the  condyles  (fig.  19).  The  clavicle  disk 
is  not  represented,  unless  it  is  by  a  narrow  free  piece  attached  to  the 
costal  angle  of  the  elytral  process,  and  represents  the  parapterum  or 
extensor  plate,  to  which  the  extensor  muscle  is  attached. 

INTERNAL    ANATOMY. 

While  some  study  has  been  made  of  the  internal  anatomy  of  these 
he<> ties  it  has  not  been  sufficient  to  warrant  a  detailed  discussion  in 
this  connection. 

79980—09 5 


52 


THE   SCOLYTID   BEETLES. 


DIGESTIVE    SYSTEM. 

The  general  character  of  the  digestive  system  is  shown  in  figure 
35,  and  no  further  explanation  is  necessary  in  this  connection  than 
that  given  in  the  legend  under  figures  35  and  36.  In  figure  36  some 
of  the  details  of  the  internal  anatomy  of  the  fore  intestine  are  shown, 

and  especially  the  structures  and 
elements  of  the  proventriculus  and 
hypopharynx. 

,  SECONDARY  SEXUAL   CHARAC- 
TERS. 

While  there  are  certain  clearly 
defined  secondary  sexual  characters 
in  these  beetles,  they  have  not  been 
recognized  by  other  writers,  and 
they  were  not  found  by  the  present 
writer  until  after  much  detailed 
study  of  the  genus.  When  they 
were  determined  it  was  surprising 
how  such  prominent  characters 
could  have  been  overlooked.  Thus 
we  have  another  example  of  how 
thoroughly  familiar  one  must  be 
with  a  given  group  in  order  to  rec- 
ognize and  properly  interpret  the 
significance  of  characters  in  struc- 
ture, sculpture,  vestiture,  etc.  In 
the  first  subdivision  of  the  genus 
the  females  are  distinguished  by  at 
transverse  ridge  across  the  anterior 
area  of  the  pronotum,  while  the; 
males  are  distinguished  by  the  ab- 
sence of  this  ridge  and  by  more 
prominent  frontal  tubercles  which 
are  separated  by  a  deeper  frontal; 
groove. 

In   the   second  subdivision    the 
females   are  distinguished   by  thei 
smoother  and  more  shining  ely tral  I 
declivity.     In  the  third  subdivision 
the  females  have  the  elytral  declivity  distinctly  more  rugose,  while 
that  of  the  males  is  smooth  and  shining.     Thus  we  have  a  reversal 
of  the  secondary  sexual  characters  within  the  same  genus,  which  is 
an  unusual  occurrence. 


•Rectum 


FIG.  35.—Dendroctonus  valens:  Digestive  organs 
of  adult.  A,  Fore  intestine;  B,  mid  intestine; 
C,  hind  intestine;  a,  anterior  section  of  mid  in- 
testine; b,  median  section  of  mid  intestine;  c, 
posterior  section  of  mid  intestine;  d,  coacal 
glands;  e,  ileum  or  small  intestine;  /,  base  of  4 
malpighian  tubes;  g,  base  of  2malpighian  tubes. 
(Original.) 


THE   GENUS   DENDROCTOX  I'S. 


53 


In  the  fourth  subdivision  the  sexes  are  more  difficult  to  recognize, 
but  the  males  are  distinguished  by  stouter,  more  opaque  mandibles, 
broader  front,  and  by  a  narrower  and  more  elongate  antennal  club. 
Whenever  there  is  doubt  as  to  the  sex  of  an  individual  it  can  be  settled 
by  examining  the  pygal  segments  for  the  characters  shown  in  figures 
2:5  and  24. 


Fi<;.  W.—Dtndroctonus  valens:  Fore  intestine,  showing  details.  A,  Fore  intestine;  B,  transverse  section 
ofproventriculus;  C,  longitudinal  section  of  same;  D,  single  plate;  E,  teeth;  F,  plates;  O,  hypopharynx; 
o,  muscles;  b,  proventricular  teeth;  c,  posterior  condyle  of  mandibular  articulation;  d,  median  fossa 
of  same;  e,  anterior  condyle  of  same; /,  hypopharyngealbracon;  g,  anterior  margin;  h,  hypopharyngeal 
papilli.  (Original.) 

PUPA. 

The  general  structure,  proportions,  and  anatomical  details  of  the 
Dendroctonus  pupa  are  shown  in  figures  37  and  38. 

Among  the  distinctive  generic  characters  are  the  large  prominent 
head  and  broad  pronotum,  while  among  the  divisional  and  specific 
characters  are  the  sculpture,  armatures,  etc.,  of  the  head,  pronotum, 
elytra,  and  abdominal  segments,  as  shown  in  the  figures  and  defined 
in  the  synoptic  tables  and  descriptions. 


54 


THE   SCOLYTID   BEETLES. 


Head.—  The  elements  of  the  adult  head  recognizable  in  the  young  pupa 
are  the  antennae,  mandibles,  maxillae,  labium,  and  what  appears  to 
be  a  well-developed  labrum,  which  extends  to  the  middle  of  the  man- 
dibles. Evidently,  however,  this  does  not  represent  the  labrum  or 
even  the  clypeus,  but  is  a  pad  to  accommodate  the  development  of 


the  long  epistomal  bristles.  The  frontal  spines  in  examples  repre- 
senting different  divisions  and  species  are  variable  in  size  and  position 
and  are  of  considerable  taxonomic  importance.  The  antennae  do  not 
extend  to  the  base  of  the  pronotum  or  scarcely  beyond  the  mouth 
parts,  and  the  club  does  not  extend  beyond  the  lateral  margins  of  the 
pronotum. 


TIIK    GENUS    DENDROCTONUS. 


55 


J'rotln>r<i.i'  'Flic  form  of  the  pronotum  corresponds  to  that  of  the 
adult  and  its  relative  proportions  are  of  some  value  in  distinguishing 
the  species.  The  number  and  position  of  the  frontal  spines  are 
fairly  constant  in  a  species,  although  they  vary  in  prominence  with 


Suture'* 


tcvral  suture 
-Hypopkurite  8 


\     ^Tleurili'Epipleuritc  10 
\lStcrnitetO 

l-n..:',^.—Dcndroctonus  valens:  Abdomen  of  pupa,  lateral  and  anal  aspects,  a,  Prescutal  lobe;  b,  scutal 
lob;  :  c.  sc-utellar  lobe;  d,  postscutollar  area;  e,  su^raanal  lobe;/,  paranal  lobe;  j,infraanal  lobe;  g^pleural 
spines;  r,  caudal  spine  or  epipleural  s;jine  of  the  9th  segment;  t,  lateral  spines;  /,  dorsal  spines;  u,  anal 
opening;  10,  tenth  segment.  (Original.) 

the  age  of  the  individual,  as  do  other  spines  of  the  body,  being  much 
less  prominent  in  the  older  or  preimaginal  stage. 

Mesoihorax. — The    mesotergum    is    subrectangular    and    without 
special  characters,  except,  perhaps,  in  the  number  and  arrangement 


56  THE  SCOLYTTD  BEETLES. 

of  the  spines.  The  median  process  of  the  scutellum  is  prominent  and 
the  posterior  or  scutellar  ridge  is  distinct.  The  base  of  the  elytra  is 
oblique  and  elevated,  and  its  integument  continuous  with  that  of  the 
tergum  and  scutellar  ridge.  The  sternum  is  situated  between  the 
mesocoxse  and  the  trochantins  of  the  prothoracic  leg. 

Metafhorax. — The  metatergum  is  prominent  and  has  the  usual  dor- 
sal or  scutellar  groove.  The  transverse  posterior  or  scutellar  ridge  is 
distinct  and  joined  at  its  ends  with  the  basal  angle  of  the  wing  pads. 
Each  of  the  scutal  lobes  bears  a  pair  of  spines.  It  differs  from  the 
metatergum  of  the  adult  mainly  in  the  absence  of  the  prescutum  and 
postscutellum,  as  defined  by  external  elements. 

Abdominal  tergites  (fig.  38). — There  are  nine  tergites  visible  dor- 
sally  and  a  very  small  tenth  visible  ventrally.  Tergites  3  to  6  are 
armed  more  or  less  distinctly  with  dorsal,  lateral,  and  pleural  spines. 
The  dorsal  spines  are  located  each  side  of  a  narrow  dorsal  groove; 
the  pleural  spines  on  the  epipleura  posterior  to  the  spiracles,  and  the 
lateral  spines  are  situated  between  the  dorsal  and  pleural.  The  size 
of  the  pleural  spines  and  the  size  and  number  of  the  dorsal  and  lateral 
ones  are  quite  variable  and  of  considerable  importance  in  defining 
the  minor  divisions.  Tergites  7  and  8  are  usually  unarmed,  but,  as 
in  the  adults,  show  sexual  differences  in  their  relative  prominence; 
9  has  the  median  lobe  short,  but  the  pleurites  are  greatly  enlarged 
and  each  is  armed  with  a  prominent  caudal  spine. 

The  four  transverse  divisions  of  the  segments  are  quite  clearly  indi- 
cated in  tergites  1  to  6.  Tergites  7  and  8  show  two  divisions,  the  first 
representing  prescutal  and  the  second  the  scutal  and  scutellar  com- 
bined, while  tergites  9  and  10  are  undivided.  It  is  interesting  to 
note  that  the  dorsal  and  pleural  armatures  are  borne  by  what  is  evi- 
dently the  scutellar  division,  and  that  the  spiracles  are  in  the  prescutal 
division,  thus  indicating  that  the  prescutal  represents  the  first  pri- 
mary division  and  the  combined  scutal,  scutellar,  and  postscutellar 
represent  the  second  primary  division. 

Abdominal  sternites. — There  are  eight  exposed  abdominal  sternites. 
These  are  sternites  3  to  10,  1  and  2  being  concealed  beneath  the 
metacoxse,  as  shown  in  figure  38. 

Abdominal  pleurites. — Epipleurites  and  hypopleurites  1  to  8  are 
clearly  defined  in  the  removed  abdomen  (fig.  38),  but  in  9  and  10  only 
the  epipleurites  are  represented,  as  indicated  by  the  pleural  suture. 
The  pleural  suture  is  distinct  to  the  ninth  segment,  where  it  joins  the 
lines  marking  the  dorsal  and  ventral  limits  of  the  pleural  division. 

Spiracles. — There  are  nine  spiracles  in  each  side  of  the  body,  one 
large  mesothoracic  spiracle  situated  between  the  posterior  lateral 
margin  of  the  prothorax  and  the  anterior  ventral  angle  of  the  elytral 
pad,  and  eight  abdominal  ones,  each  in  its  respective  epipleurite. 


Till:    GENUS   DENDROCTONUS.  57 

The  metathoracic  spiracle  is  not  represented.  Spiracles  3  to  8  are 
exposed  when  the  elytral  pad  is  in  normal  position,  but  spiracles  7 
and  8  are  very  small  and  obscure.  Thus  the  pupa  has  the  same 
number  of  spiracles  as  the  larva,  while  in  the  adult  there  is  an  addi- 
tional one,  although  that  of  the  eighth  abdominal  tergite  is  apparently 
^rudimentary.  The  larva  has  one  thoracic  spiracle,  apparently  in  the 
prothoracic  segment.  The  pupa  has  one  in  the  mesothoracic,  and  the 
adult  has  one  in  the  mesothorax  and  one  in  the  metathorax. 

Legs. — The  front  and  middle  legs  are  exposed,  while  the  hind  legs 
are  partially  concealed  beneath  the  elytra  and  wing  pads.  The  front 
coxae  are  large  and  contiguous,  the  anterior  fourth  covered  by  the 
maxillae  and  labium,  and  the  posterior  margin  extends  over  the 
anterior  margin  of  the  mesosternum.  The  middle  coxae  are  partially 
hidden  by  the  apex  of  the  front  tibia  and  its  tarsus.  The  hind 
coxa1  are  for  the  most  part  exposed,  and  distinctly  separated  by  an 
iniercoxal  area.  The  positions  of  the  different  parts  of  the  legs  in 
their  relation  to  the  exposed  structures  are  shown  in  figure  37,  and 
are  of  considerable  taxonomic  importance.  The  apical  and  subapical 
spines  of  the  femora  are  also  of  considerable  importance  as  distinc- 

;    tive  characters. 

LARVA. 

The  structure  and  general  characters  of  the  larva  are  shown  in 
figure  39.  It  is  of  the  subcylindrical,  wrinkled,  legless  type  common 
to  all  of  the  true  Rhynchophora,  and  also  has  the  form  of  mouth  parts 
characteristic  of  the  larvae  of  this  suborder.  There  are  three  thoracic 
and  ten  abdominal  segments,  the  tenth  being  represented  by  the 
anal  lobes.  The  four  longitudinal  divisions,  viz,  one  sternal,  two 
pleural,  and  one  tergal,  are  clearly  represented  in  all  of  the  segments. 
The  tergal  division  occupies  nearly  one-half  of  the  circumference, 
the  two  pleural  divisions  together  about  one-fourth,  and  the  sternal 
division  slightly  more  than  one-fourth.  The  head  is  much  narrower 
than  the  first  thoracic  segment  and  but  slightly  longer.  The  three 
thoracic  segments  together,  or  the  thorax,  is  about  one- third  as  long 
as  the  abdomen.  With  the  exceptions  of  the  scattering  hairs  on  the 
head  and  on  the  scutellar  lobes  of  the  thoracic  and  abdominal  seg- 
ments, the  body  is  without  distinguishing  vestiture. 

EXTERNAL    CHARACTERS. 

Head  (figs.  40,  41). — The  head  is  by  far  the  most  important  part  of 
the  body  as  a  bearer  of  taxonomic  characters  in  the  larva.  The  gen- 
eral structure  is  shown  in  figure  40,  and  the  anatomical  details  in 
figures  41  and  42.  All  of  the  primary  elements  of  the  adult  head  are 
represented,  but  they  are  much  more  simple  in  their  structural  details. 
The  more  striking  differences  in  the  larval  head  are  found  in  the 


58 


THE   SCOLYTID   BEETLES. 


presence  of  clearly  defined  front,  clypeus,  and  labrum,  in  the  articu- 
lation of  the  mandibles,  and  in  their  rudimentary  hypostoma. 

Labrum  (figs.  40,  41). — The  labrum  is  prominent,  the  dorsal  area 
twice  as  broad  as  long,  about  one- third  narrower  than  the  clypeus,  | 
but  nearly  as  long,  with  the  apical  margin  broadly  rounded,  truncate 


or  faintly  emarginate,  and  with  several  apical  papillae.  The  median 
dorsal  area  bears  several  long  hairs  and  two  slightly  elevated  dark  spots 
where  the  epipharyngeal  bracons  are  attached.  The  latter  somewhat 
resemble  the  mandibular  hooks  of  dipterous  larvae,  and  may  or  may 
not  represent  paired  elements  of  the  head  of  a  primitive  arthropod. 


Till':    CKNTS   DENDROCTONUS. 


59 


Whatever  their  origin  may  have  been,  the  present  function  is  to  sup- 
port the  epipharynx  and  also  serve  as  chitinous  attachments  for  the 
depressor  muscles  of  the  labrum.  They  are  covered  by  the  epipharynx 
and  extend  down  and  back  to  the  oesophagus  and  to  a  point  beneath 
the  base  of  the  clypeal  area. 


Epimmial  nturt' 


•  Occiput-' 


4Q.—Dendroctonusvalens:  Head  of  larva.    A,  Trans  verse  section;  B,  oral  aspect;  C,  ventral  aspect;  D,        \j 
lotiKitu  Jiiial  section;  E,  dorsal  aspect;  a,  muscles;  b,  submental  lobe;  c,  maxilla;  d,  condyle  of  dorsal  articu- 
lation of  mandible ;  c,  pleuix>stQma^Jiypopharvngeal  bracon:g.  fossa  of  ventral  articulation  of  mandifcls^— i       j 
h,  maxillary  condyle;  iJKular plate;77«iaxillary  foramen ;  jj,  oral  foramen;  k,  attachment  of  epipharyngeal  ^Tl/'t 
bracons(labralhooks)f^pregenalarea;  m,  g**ie*area;  ra/,g**to»apodeme;  n,  attachment  of  labial  muscle; 

0,  frontal  apodeme;  p,  integumental  attachmeirfcsjj'  occipital  ipodeme;  r,  frontal  apex;  *,  frontal  suture; 

1,  j)rcscutal  lol>e  of  mesothoracic  segment;  u,  scutelhH^pbe  ofprothoracic  segment:  v,  prescutal  lobe;  w, 
hypopharyngeal  bracon;  x,  sternal  section  of  prothorachss^gm^nt;  y,  sternellar  section  of  mesothoracic 
segment,  both  distorted;  z,  apical  papilli.    (Original.) 

Clypeus. — The  so-called  clypeus  evidently  does  not  represent  an 
entirely  distinct  element,  but  a  produced  dilated  preepistomal  area 
or  extension  of  the  epistoma  proper.  In  Dendroctonus  larvae  it  is 
twice  as  broad  as  long  and  narrowed  toward  the  apical  margin, 
which  is  usually  slightly  emarginate.  The  basal  connection  with  the 
epistoma  is  continuous  and  rigid,  and  bears  two  widely  separated 
bristles  near  the  base.  The  sides  are  rounded  to  a  rather  acute  im- 
pressed basal  angle  at  the  mandibular  condyle. 


60 


THE   SCOLYTID   BEETLES. 


Epistoma. — The  epistoma  is  quite  clearly  defined  as  a  thickened 
transverse  area  between  the  clypeus  and  the  frontal  area.  It  does 
not  extend  laterally  to  the  frontal  sutures,  but  the  ends,  where  they 
join  the  pleural  ridge  or  pleurostorna,  bear  the  condyles  for  the  dorsal 
articulation  of  the  mandibles.  As  in  the  adults,  this  area  is  quite  vari- 


able within  the  genus.  It  is  elevated  to  flat,  with  the  anterior  margin 
ranging  from  curved  to  nearly  straight  and  the  lateral  angles  elevated 
or  slightly  produced  so  as  to  form  the  rigid  support  for  the  dorsal 
condyles. 

Hypostoma. — The  hypostoma  is  not  represented  by  an  exposed 
piece,  but  by  the  apodeme  which  forms  the  thickened  lateral  and  sub- 


THK    UENUS   DENDROCTONUS.  61 

lateral  margins  of  the  maxillary  foramen.  The  anterior  end  supports 
the  fossa  (g)  of  the  ventral  articulation  for  the  mandible,  and  the 
ventral  end  supports  the  condyle  for  the  articulation  of  the  maxillary 
cardo.  It  is  connected  across  the  gular  space  by  the  entogular  plate. 

Pleurostoma  (fig.  40,  e). — The  pleurostoma  is  represented  by  the 
thickened  lateral -margin  of  the  oral  foramen.  The  dorsal  end  con- 
tributes to  the  rigid  support  of  the  dorsal  articulation  for  the  mandible 
and  the  ventral  end  to  that  of  the  ventral  articulation. 

Front. — The  front  is  situated  posterior  to  the  epistoma  and  between 
oblique  sutures  which  converge  from  the  anterior  angles  to  the 
epicranial  suture.  The  median  area  is  quite  variable  within  the  genus. 
It  may  be  flat  and  smooth  to  elevated.  In  the  latter  case  it  may  be 
small,  smooth,  and  convex,  or  prominent,  transverse,  and  rugose. 

Epicranium. — The  epicranium  is  represented  by  the  dorsal  areas 
of  the  two  large  lobes  each  side  of  the  distinct  epicranial  suture  and 
frontal  area.  These  lobes  are  continuous  throughout  the  occipital 
and  genal  areas  and  accommodate  the  very  large  retractor  muscles 
of  the  mandible.  The  genal  areas  are  connected  by  the  broad  ento- 
gular plate. 

Occipital  foramen. — The  occipital  foramen  is  situated  in  the  pos- 
terior ventral  section  of  the  head  and  occupies  about  one-half  of  the 
ventral  area.  It  is  bounded  posteriorly  and  laterally  by  a  broad 
entoccipital  rim  and  anteriorly  by  a  subchitinous  rim.  The  occipital 
apodeme  arises  from  the  posterior  margin,  and  extends  anteriorly 
immediately  beneath  the  epicranial  suture. 

Entogular  plate  (fig.  40,  i). — The  entogular  plate  is  the  subchitinous 
plate  which  forms  the  entocranial  connection  between  the  genal  areas 
and  anteriorly  between  the  lateral  sections  of  the  hypostoma.  It  is 
covered  by  the  submental  lobe,  part  of  the  muscles  of  which  are  at- 
tached to  the  posterior  angles  and  posterior  margin. 

Maxillse  (fig.  41). — The  maxillae  are  quite  simple  in  structural 
details.  The  cardo  is  present  and  distinct.  Its  basal  articulation 
and  attachment  are  by  ligaments  and  a  fossa  to  a  condyle  supported 
by  the  hypostomal  apodeme.  Its  anterior  attachment  to  the  stipes 
is  by  articulating  membrane.  The  median  section  is  not  divided  into 
stipes,  subgalea,  and  palpifer,  but  is  one  continuous  piece  with  the 
anterior  inner  angle  produced  into  a  lacinial  lobe  which  is  armed  with 
a  number  of  papillae  situated  on  a  membranous  integument.  The 
palpus  is  2-jointed  and  telescopic  as  usual.  The  relative  proportions, 
sculpture,  and  vestiture  are  shown  in  the  figure. 

Ldbium. — The  labium  of  the  larva  is  very  different  in  structure 
from  that  of  the  adult.  The  submentum  is  represented  by  a  lobe 
which  is  very  broad  and  differs  but  slightly  from  the  sternal  lobe  of 
the  prothoracic  segment  with  which  its  posterior  integument  is 
directly  connected.  The  lateral  integument  is  continuous  with  that 


62  THE  SCOLYTID  BEETLES. 

of  the  maxilla  and  the  anterior  angles  are  extended  forward  to  the 
base  of  the  palpi.  The  mentum  is  represented  by  the  median  tri- 
angular chitinous  plate,  the  posterior  section  of  which  is  produced 
and  narrowed,  and  the  anterior  median  section  is  produced  ante- 
riorly between  the  palpi  and  supports  the  ligula.  The  short,  conical, 
2-jointed  palpi  are  situated  on  the  anterior  angles  of  the  mentum 
and  are  scarcely  longer  than  the  simple  lobelike  ligula  which  bears  a 
few  simple  papillae. 

HypopJiarynx  and  epipharynx. — The  position  and  character  of  these 
important  elements  of  the  oral  opening  are  shown  in  figures  40,  D, 
and  41,  B. 

Mandibles  (fig.  42). — The  mandibles  are  stout,  with  the  laterodorsal 
surface  rugose,  except  toward  the  apex,  which  is  produced  into  an 
apical  tooth;  the  inner  edge  toward  the  apex  is  provided  with  a  sub- 
apical  tooth  and  two  small  irregular  medial  teeth.  The  condyle  of 
the  ventral  angle  is  globular  and  fits  into  the  concave  fossa  (fig.  40,  g) 
of  the  hypostoma,  while  in  the  dorsal  articulation  the  fossa  is  borne 
by  the  mandible  and  the  condyle  by  the  epistoma  (fig.  40,  d) .  The 
small  extensor  muscle  is  attached  to  the  outer  basal  margin  midway 
between  the  condyles,  while  the  large  and  powerful  retractor  muscle 
is  attached  to  the  margin  of  the  more  produced  inner  angle,  thus 
giving  a  direct  lateral  motion  to  the  mandibles. 

Tergites  (fig.  39). — The  dorsal  area  of  the  tergum  of  the  prothoracic 
segment  is  undivided,  but  evidently  represents  the  scutum  (e)  and 
scutellum  (/) .  The  dorsal  area  of  the  mesothoracic  and  metathoracic 
segments  has  two  divisions.  The  anterior  division  evidently  repre- 
sents the  prescutal  lobe  (g}.  There  is  evidence  of  a  scutal  lobe  (e)  on 
the  lateral  area  of  both  segments,  as  indicated  in  the  abdominal  ter- 
gites,  where  the  scutal  lobe  appears  between  the  anterior  and  the 
posterior  lobe.  Thus  the  latter  evidently  represents  the  scutellar 
division,  or  scutellar  lobe  (/). 

Sternites. — The  sternum  of  each  of  the  segments  has  three  sections,  ] 
anterior,  median,  and  posterior,  or  sternal  (Ji\  sternellar  (i),  and  post- 
sternellar  (j).  In  the  thoracic  segments  the  sternal  is  the  larger  and 
projects  posteriorly  over  the  middle  of  the  sternellar  lobe,  which  is 
represented  by  a  coxal  lobe  each  side  of  the  sternal  section.  In 
some  of  the  species  these  lobes  have  a  median  chitinous  spot  or  foot 
callus  at  the  point  where  a  foot  occurs  in  the  legged  larvae  of  other 
Coleoptera.  The  abdominal  sternites  have  the  same  number  of  sec- 
tions, but  the  sternellar  section  irs  not  covered  by  the  sternal. 

Pleurites. — The  pleurum  of  each  segment  is  divided  longitudinally 
by  an  irregular  pleural  groove  or  suture  (w) .  The  lobe  immediately 
below  the  groove  at  the  end  of  the  sternites  may  be  referred  to  as  the 
hypopleural  (&)  and  that  immediately  above  it  as  the  epipleural  (Z). 
The  hypopleura  of  the  thoracic  segments  represent  the  episternurn, 


THE   GENUS   DENDROCTONUS. 


63 


Miid  the  epimerum  is  obscurely  represented  by  the  epipleura,  both 
of  which  are.  but  little,  if  at  all,  different  from  those  of  the  abdomen. 
The  epipleural  lobe  of  the  prothoracic  segment  has  a  spiracle,  while 
(hose  of  the  mesothoracic  and  metathoracic  segments  are  without  a 
spiracle,  but  has  lateral  lobes  or  areas  for  the  embryonic  wing. 

Sf tirades. — It  will  be  noted  in  figure  39  and  Plate  VITI  that  the 
prothoracic  segment  has  a  spiracle  situated  on  the  epipleurite  near 


FIG.  42.— Dendroctonus  valens:  Mandibles  of  larva.  A,  Latero-dorsal  aspect;  B,  dorsal  aspect;  C,  lateral 
aspect;  D,  apical  aspect;  a,  apical  tooth;  b,  subapical  tooth;  c,  median  tooth;  d,  molar  tooth;  e,  extensor 
tendon;  /",  retractor  muscle  disk;  g,  retractor  muscle;  h,  extensor  muscle;  i,  dorsal  fossa;  j,  dorsal  condyle; 
^,  ventral  condyle;  I,  basal  ridge.  (Original.) 

the  epipleurite  of  the  mesothoracic  segment.  The  writer  is  not  cer- 
tain as  to  whether  or  not  this  really  belongs  to  the  prothoracic  seg- 
ment or,  as  in  the  abdomen,  to  the  anterior  or  prescutal  division  of 
the  mesothoracic  segment.  The  metathoracic  segment  is  plainly 
without  spiracles,  but  the  abdominal  segments  1  to  8,  inclusive,  have 
spiracles  which  are  more  or  less  distinct,  being  rather  obscure  in  the 
first  division  and  in  section  a3  (see  PI.  I)  and  without  lateral  tuber- 
cles, while  in  section  a4  and  subdivision  D  both  the  spiracles  and 


64  THE  SCOLYTID  BEETLES. 

spiracular  tubercles  (Plate  VIII)  are  distinct.     The  ninth  segment  is 
without  spiracles. 

Chitinous  plates. — In  some  species  (division  I)  there  are  no  distinct 
chitinous  plates  or  tubercles,  while  in  others,  section  a4  and  subdi- 
vision D,  they  are  present  and,  excepting  Dendroctonus  mica  us, 
become  more  distinct  toward  and  including  subdivision  D,  in  which 
the  dorsal  plates  of  the  eighth  and  ninth  abdominal  segments  are 
distinctly  armed. 

DIGESTIVE    SYSTEM. 

The  peculiar  characters  of  the  digestive  system  of  the  larva  are 
illustrated  in  figure  43,  showing,  at  right,  a  median  longitudinal  sec- 
tion through  the  body  from  the  oral  to  the  anal  opening.  In  every 
respect  the  anatomical  details  of  the  digestive  system  are  much  more 
simple  in  the  larva  than  in  the  adult.  The  same  primary  divisions 
(^  fore,  middle,  and  hind  intestine  are  represented  and  there  is  the 
same  number  of  malpighian  tubes,  but  the  fore  intestine  is  very  simple 
as  compared  with  that  of  the  adult,  the  crop  and  proventriculus  being 
scarcely  different  in  general  details  from  the  oesophagus. 

EGGS. 

The  eggs  of  Dendroctonus  have  not  been  studied  in  detail,  but  they 
are  short,  oval  to  oblong-oval,  pearly  white  and  shining,  and  appar- 
ently without  distinctive  generic  or  specific  characters. 

PHYSIOLOGICAL   CHARACTERISTICS. 

In  addition  to  the  morphological  characters  which  serve  to  distin- 
guish the  genus,  there  are  certain  physiological  characteristics  pecul- 
iar to  the  species  of  the  genus  which  serve  as  additional  evidence  of 
distinction.  Indeed,  it  becomes  more  and  more  evident  that  a  cor- 
rect interpretation  of  natural  groups  of  individuals,  termed  species, 
and  natural  groups  of  species,  termed  genera,  must  be  based  not  alone 
on  a  common  plan  of  structure  or  similarity  in  one  or  more  anatomical 
elements,  but  that,  in  order  to  come  nearer  the  truth,  the  morpho- 
logic evidence  of  specific  distinction  must  be  supplemented  by  physio- 
logic and  bionomic  evidence.  Some  of  the  physiological  features 
common  to  the  species  of  this  genus,  and  more  or  less  peculiar  to  them, 
are  found  in  the  character  of  their  brood  galleries,  in  their  habit  of 
attacking  living  trees,  in  their  concentration  of  effort  to  overcome  the 
resistance  exerted  by  the  tree  attacked,  and  especially  by  their  ability 
to  manipulate  and  to  dispose  of  the  quantities  of  resin  which  flow 
into  their  burrows  in  the  living  bast  and  cambium;  lastly,  in  their  in- 
timate bionomic  relations  to  definite  genera  and  species  of  conifers. a 

a  See,  also,  physiological  characteristics  of  the  species,  as  given  in  the  forthcoming 
Bulletin  No.  83,  Part  I,  which  deals  with  the  bionomic  and  economic  features,  and 
other  characteristics  peculiar  to  the  major  and  minor  divisions  as  denned  in  the  syn- 
optic tables  of  galleries,  host  trees,  and  distribution  in  the  present  paper  (pp.  76-79). 


THE   GENUS  DENDROCTONUS. 


65 


Epistoma^ 
Clypeus 
Labrum-t- 


Head 


FIG.  43.—Dendroctonv3  valens:  Digestive  organs  of  larva. 
A  ,  Fore  intestine;  £,  mid  intestine;  C,  hind  intestine; 
a,  mouth ;  6,  anterior  section  of  mid  intestine;  c,  median 
section;  d,  posterior  section;  e,  small  intestine;/,  ccecal 
glands;  g,  anus;  9th,  ninth  segment;  10th,  tenth  segment; 
ft,  base  of  the  2  malpighian  tubules;  i,  base  of  the  4 
malpighian  tubules.  (Original.) 


66  THE  SCOLYTID  BEETLES. 

SPECIFIC   DISTINCTIONS. 

In  the  literature  on  Scolytidse,  and,  for  that  matter,  on  almost  any 
group  of  insects  of  special  systematic  and  economic  importance,  there 
is  much  confusion,  due  to  different  interpretations  of  specific  distinc- 
tion. Some  authors  have  combined  many  described  species  into  one, 
while  others  have  recognized  many  distinct  forms  among  those  here- 
tofore included  in  one  species,  and  have  proposed  as  many  different 
names  for  them.  It  is  evident  that  whenever  " lumping"  or  " split- 
ting" is  necessary  for  the  clear  definition  and  recognition  of  a  species 
it  should  be  done,  but  it  is  equally  evident  that  neither  should  be 
attempted  without  an  adequate  knowledge  of  at  least  the  genus  rep- 
resented, in  order  that  the  true  characters  of  specific  distinction  may 
be  recognized  from  those  which  serve  to  distinguish  the  genus  or  the 
major  and  minor  divisions  of  higher  rank  than  the  species. 

RANGE  OR  LIMITS  OF  SPECIFIC  VARIATION. 

The  determination  of  the  range  or  limits  of  variation  in  characters 
utilized  for  the  distinction  of  a  species  is  one  of  the  most  troublesome 
questions  with  which  the  system atist  has  to  deal.  With  one  or  a  few 
specimens  the  line  separating  one  recognized  species  from  another  may 
be  distinct  and  definite,  but  as  the  number  of  specimens  from  different 
localities  increases  the  line  of  distinction  from  allied  forms  often 
becomes  less  and  less  distinct  until  it  is  almost  or  quite  obscure. 
Here  is  where  expert  judgment,  based  on  experience  and  a  technical 
knowledge  of  the  special  group  involved,  is  required  in  order  to  decide 
whether  or  not  two  heretofore  recognized  and  closely  allied  species 
should  be  kept  separate  or  be  combined.  The  recognition  of  pre- 
vailing variants  or  constants,  or  of  forms  having  abnormal  or  normal 
morphologic  and  physiologic  characters,  is  of  special  importance  in 
this  connection,  as  is  also  the  recognition  of  the  disturbing  factor  of 
parallel  modification  in  characters  and  habits  among  species  of  the 
same  genus,  as  well  as  among  those  of  different  genera. 

If  the  variants  connecting  two  allied  groups  comprise  only  a  small 
percentage  of  the  individuals,  they  may  be  considered  as  departures 
from  the  constants  of  the  species  more  nearly  represented,  and  thus 
the  groups  so  slightly  connected  will  serve  the  purposes  and  require- 
ments of  species  and  neither  of  them  should,  in  the  writer's  opinion, 
be  designated  as  a  named  subspecies,  race,  or  variety;  but  if,  on  the 
other  hand,  the  connecting  variants  comprise  a  large  percentage  of 
individuals,  and  no  other  characters  sufficiently  distinct  and  constant 
can  be  found  by  which  individuals  may  be  readily  referred  to  one  or 
the  other  of  the  heretofore  recognized  species,  it  would  indicate  that 
the  two  are  not  specifically  distinct. 


THE    GKXTS    UKNDKOCTONUS.  67 

PROGRESSIVE  MODIFICATIONS. 

The  writer  has  been  forcibly  impressed  with  the  prevailing  princi- 
ple of  progressive  modification  in  relative  proportions  in  form  and 
structural  details  in  scolytid  and  other  beetles.  Whenever  these 
modifications  in  relative  proportions  are  available  for  the  statistical 
method  of  analysis  it  is  often  possible  to  express  in  numbers  the  dif- 
ference between  species  and  to  indicate  clearly  the  lines  of  modification 
and  rates  of  departure  among  the  species  of  a  genus  or  larger  group. 

There  are  some  good  examples  of  this  principle  of  progressive  modi- 
fication in  the  genus  Dendroctonus,  which  is  manifested  not  alone  in 
the  adults,  but  in  the  pup  as,  larvae,  and  character  of  work,  and  it  is 
most  interesting  and  significant  to  note  that  the  modifications  are  in 
the  same  general  direction  in  all  cases.  When  the  species  are  ar- 
ranged in  the  order  indicated  by  these  modifications  and  other  char- 
acters, the  species  of  the  first  division  to  the  last  of  those  of  the 
second  division  are  found  to  be  modified  from  small  to  larger  size, 
the  extremes  being  represented  by  D.  frontalis,  with  the  minimum 
length  of  2.5  mm.,  to  D.  valens,  with  the  maximum  length  of  9 
mm.  Naturally  we  find  the  same  rate  of  difference  in  size  of  the 
immature  stages  and  galleries.  This  same  tendency  toward  increased 
size  is  manifested  within  each  subdivision,  section,  or  minor  group  of 
allied  forms  and  appears  to  be  a  prevailing  principle  throughout  the 
Scolytidse,  and  thus  serves,  in  connection  with  other  lines  of  modifica- 
tion, as  one  of  the  first  guides  to  a  natural  arrangement  or  classifica- 
tion of  the  species.  In  Dendroctonus  the  progressive  modification  of 
characters  other  than  size  is  shown  or  indicated  as  follows: 

PROGRESSIVE  MODIFICATION  OF  CHARACTERS  IN  THE  GENUS  DENDROCTONUS. 

ADULTS. 

Primary  characters. 

Body  slender  to  stouter. 
Head  large  to  smaller. 
Prothorax  long  to  shorter. 

Pronotum  with  sides  nearly  parallel  to  distinctly  narrowed  or  constricted  anteriorly. 
Pronotum  as  broad  as  elytra  to  narrower. 

(A  mean  composite  ratio  of  the  above  gives  a  number  which  expresses  the  relative 
proportions  and  serves  as  a  species  index.) 
Front  grooved  and  tuberculate  to  convex  and  smooth. 
Elytra  without  long  hairs  to  long  hairs  over  entire  surface. 
Tibia  from  slender  to  broader  with  a  tendency  to  dilate  toward  the  apex, 
Funiculus  of  antenna  with  second  joint  long  to  shorter. 

Secondary  sexual  characters. 

Front  of  head  with  sexual  differences  to  similar  or  alike  in  both  sexes. 
Pronotum  with  sexual  differences  to  alike  in  both  sexes. 
Elytral  declivity  without  sexual  differences  to  distinct  differences. 
Declivity  rugosities  small  to  coarse,  smooth  in  female  to  coarse  in  male  or  reversed. 
Mandibles  alike  or  similar  in  both  sexes,  to  much  stouter  in  the  male. 
79980—09 6 


68  THE    SCOLYTID    BEETLES. 

PUP^E. 

Front  of  head  grooved  to  convex. 
Body  spines  small  to  coarse. 

LARV.E. 

Body  simple,  without  chitinous  plates  or  hairs,  to  distinct  chitinous  plates  and  more 
prominent  hairs. 

Eighth  and  ninth  abdominal  segments  without  chitinous  plates  to  with  plates,  these 
last  unarmed  to  armed. 

Spiracles  simple  to  complex,  smooth  to  tuberculate. 

Epipleurites  without  tubercle,  to  prominent  tubercle. 

GALLERIES. 

Long  and  winding  to  short  and  straight. 

Eggs  isolated  to  grouped  and  massed. 

Larval  mines  hidden  to  exposed  and  short  to  long. 

HOSTS. 

From  one  genus  to  many  genera,  and  from  one  species  to  many  species. 
D.  brevicomis  is  found  in  pine  only,  while  D.  valens  infests  Pinus,  Picea,  and  Larix; 
D.  simplex  infests  Larix  only,  and  D.  pseudotsugx  infests  Pseudotsuga  and  Larix. 

DISTINCTION  OF  MAJOR  AND   MINOR  DIVISIONS  OF  THE  GENUS. 

In  a  comparative  study  of  the  species  of  the  genus  to  determine 
their  relative  positions,  as  indicated  by  degrees  of  resemblance  or  dif- 
ference, they  are  found  to  fall  according  to  progressive  modification  of 
characters  into  major  and  minor  divisions,  which  may  be  designated  as 
divisions,  subdivisions,  sections,  subsections,  series,  and  subseries,  to 
the  smallest  practicable  minor  division  of  the  genus,  viz,  the  species.  ;| 

In  this  classification  of  the  genus  the  rank  of  a  primary  division  may 
be  that  of  the  subgenus  of  some  authors  and  the  lower  series  of  closely 
allied  species  may  be  recognized  by  some  systematists  as  occupying 
the  rank  of  subspecies,  races,  or  varieties;  but  the  writer  has  been 
guided  by  the  belief  that  the  principle  of  a  less  restricted  range  of1 
generic  and  more  restricted  range  of  specific  distinction  will  contribute 
toward  a  more  correct  knowledge  of  the  forms  of  life  than  if  the 
reverse  principle  is  followed. 

The  classification  of  the  species  of  a  genus  into  major  and  minor  | 
divisions  is  necessarily  arbitrary,  and  is  subject  to  changes  as  may 
be  suggested  by  increased  knowledge  and  the  addition  of  species. 
To  a  more  limited  extent,  the  designation  of  a  species  is  arbitrary 
and  with  additional  material  and  information  is  subject  to  revision;  | 
but  since  the  species,  next  to  the  individual,  is  the  constant  or  unit 
of  classification  and  investigation,  it  should  represent  the  lowest  prac- 
tical division  of  a  genus  that  is  recognizable  from  a  description  of  n 
typical  form  or  by  comparison  with  the  type  on  which  the  description 
was  based. 


THE   GENUS   DENDROCTONXJS.  69 

PLAN  OF  SYNOPTIC  TREATMENT. 

The  plan  here  applied  for  the  classification  and  synoptic  treatment 
of  the  species  of  the  genus  is  one  which  appears  to  be  most  available 
and  practicable  for  the  clear  definition  of  the  progressive  modification 
of  taxonomic  characters  and  for  indicating  the  relative  systematic 
positions  and  limits  of  the  major  and  minor  divisions  and  the  species. 
It  is  not  radically  different  from  some  of  the  more  generally  adopted 
dichotomous  systems,  and  it  conforms  to  the  primary  objects  of  a 
synopsis  in  that  it  provides  (a)  for  a  direct  comparison  of  opposing 
characters,  (&)  for  a  direct  line  of  references  leading  down  to  the 
specific  characters,  or  vice  versa. 

With  this  method  of  indicating  the  supposed  natural  relation  of 
the  species,  the  described  characters  of  the  major  and  minor  divisions 
and  sections,  together  with  those  of  specific  distinction,  serve  as  a 
description  of  the  species.  Thus,  division  I,  subdivision  A,  section  a2, 
subsection  b2,  series  c2,  defines  the  characters  common  to  species 
6,  7,  and  8,  which  are  separated  by  their  respective  specific  char- 
acters. Some  additional  advantages  of  this  method  are  the  con- 
secutive arrangement  of  letters  and  figures  which  throughout  a  given 

ible  are  not  duplicated.     The  Roman  numerals  indicate  at  once  the 
tary  divisions,  the  capital  letters  the  subdivisions,  and  the  com- 

ined  small  letter  and  Arabic  numeral  the  sections,  subsections, 
series,  etc.,  to  any  desired  limit.  The  reference  from  right  margin 
to  center,  instead  of  to  left  margin,  is  also  an  advantage  in  defining 
the  limits  of  a  major  and  minor  division.  It  also  provides  for  full 

niragraphs,  thus  economizing  space  and  cost  of  printing. 

SYNOPSES  OF  MORPHOLOGICAL  AND  PHYSIOLOGICAL 
CHARACTERS. 

SYNOPSIS  OF  ADULT  CHARACTERS. 


bum  somewhat  elongate  and  as  broad  as  elytra;  not  di jtiiic tly  narrowed  ante- 
riorly except  in  subdivision  B;  anterior  dorsal  half  of  elytra  without  long  hairs. 

Division  I,  pages  69,  81. 

lotum  stout;  usually  narrower  than  elytra,  and  distinctly  narrowed  and  constricted 
anteriorly;  anterior  dorsal  half  of  elytra  normally  with  long  hairs,  except  in  tere- 
brans Division  II,  pages  71, 116. 

DIVISION-  I. 

Body  somewhat  slender,  pronotum  but  slightly  narrowed  anteriorly;  elytral  declivity 
with  second  stria  straight,  second  interspace  not  distinctly  broader  or  narrowed 
toward  apex;  head  with  frontal  groove  and  tubercles  except  in  convexifrons. 

Subdivision  A,  pages  69,  81. 

Body  stout;  pronotum  distinctly  narrowed  and  constricted  anteriorly;  elytral  decliv- 
ity with  second  stria  curved,  second  interspace  broad  and  distinctly  narrowed 
toward  apex;  head  without  frontal  tubercles  or  groove. 

Subdivision  B,  pages  71,  105. 

SUBDIVISION  A. 

Elytral  declivity  without  long  hairs Section  al,  page  70. 

Elytral  declivity  with  long  hairs Section  a2,  page  70. 


70  THE   SCOLYTID   BEETLES. 

Section  al. 

Length  3  to  5  mrn.,  brownish,  to  nearly  black;  elytral  rugosities  fine,  densely  placed, 
the  ^striae  obscure  and  but  slightly  or  not  at  all  impressed.  California,  Oregon, 

Washington,  and  Idaho,  in  Pinus 1.  brevicomis  Lee.,  page  81. 

Length  2.5  to  4.7  mm.,  brownish  to  black;  elytral  striae  moderately  to  distinctly 
impressed ;  interspacial  rugosities  moderately  coarse  and  obtuse  to  coarse  and  acute. 
Arizona,  New  Mexico,  southern  Colorado,  southern  Utah,  and  southern  California. 

2.  barberi  n.  sp.,  page  85. 
Section  a%. 

Head  without  frontal  tubercles  or  groove,  but  with  posterior  impression. 

Subsection  bl,  page  70. 

Head  with  more  or  less  prominent  frontal  tubercles  each  side  of  a  distinct  median 
groove Subsection  b2,  page  70. 

Subsection  bl. 

Length  4  to  6  mm.;  reddish-brown  to  black,  shining;  body  slender;  elytral  rugosities 
moderately  coarse  but  not  densely  placed,  except  toward  base,  the  striae  faintly 
impressed,  with  rather  coarse  indistinct  punctures;  pronotum  with  long,  erect 
hairs  on  the  entire  lateral  area;  declivity  shining.  Arizona,  New  Mexico,  south- 
ern Colorado,  and  southern  Utah,  in  Pinus 3.  convexifrons  n.  sp.,  page  87. 

Subsection  b2. 

Elytral  striae  distinctly  punctured Series  cl,  page  70. 

Elytral  striae  not  distinctly  punctured Series  c2,  page  70. 

Series  cl. 

Length  2.5  to  4  mm.;  brownish  to  black;  elytral  rugosities  obtuse,  moderately  coarse, 
not  very  densely  placed,  and  but  moderately  coarser  toward  the  base  and  vertex 
than  elsewhere;  pronotum  usually  with  a  few  long  hairs  on  the  anterior  section 
of  the  lateral  area.  Pennsylvania  to  Florida,  westward  to  Ohio  and  Texas,  in 
Pinus  and  Picea 4.  frontqlis  Zimm.,  page  90. 

Length  4  to  5  mm.;  brownish  to  black;  elytral  rugosities  subacute,  moderately  coarse 
and  distinctly  coarser  toward  the  base  and  vertex;  pronotum  with  long  erect  hairs 
on  the  anterior  half  of  the  lateral  areas;  elytra  with  long  hairs  confined  to  declivity 
and  posterior  areas.  Central  Arizona,  in  Pinus 5.  arizonicus  n.  sp.,  page  95. 

Series  c2. 
Striae  distinctly  impressed. 

Length  3  to  4.5  mm.;  brownish  to  black;  elytral  rugosities  distinctly  coarser 
toward  the  base  and  vertex,  and  with  an  evident  row  of  acute  rugosities  on  the 
first  interspace;  pronotum  •  clothed  with  stout  reclining  hairs  and  the  entire 
lateral  area  with  long,  erect  hairs;  elytral  striae  moderately  distinct.  Southern 

Mexico,  in  Pinus 6.  mexicanus  Hopk.,  page  97. 

Striae  not  distinctly  impressed. 

Length  5  to  6  mm.;  black;  elytral  rugosities  obtuse,  rather  densely *placed,  mod- 
erately coarse  toward  dorsal  suture,  fine  and  less  evident  toward  side;  striae 
obscure,  especially  on  the  side;  pronotum  distinctly  pubescent,  with  very  long 
erect  hairs  on  the  entire  lateral  area;  punctures  moderately  coarse.  Southern 

Mexico,  in  Pinus 7.  parallelocollis  Chap. ,  page  99. 

Length  4  to  7.4  mm.;  black;  elytral  rugosities  rather  coarse  and  sparse;  the  striae 
toward  the  side  rather  distinct;  pronotum  moderately  pubescent,  with  long, 
hairs  on  the  anterior  two-thirds  of  the  lateral  area;  punctures  usually  fine. 
Arizona,  New  Mexico,  southern  Colorado,  and  Utah,  in  Pinus. 

8.  approxifmatus  Dietz,  page  101. 


TIIK    GENUS    DKNDIMH'TONrs.  71 

SrBDIYIXION     P>. 

Pronotum  with  (f<rj>  punctures. 

Length  3.7  to  <;.  l  in  in.;  brownish  t<>  Muck ;  elytra  \vith  stria1  moderately  impressed. 
punctures  usually  small  or  moderately  coarse  and  distinct.  North  and  west  of 
northwestern  Colorado,  southward  i<>  Yosemite  National  Park,  California,  in 

/'in </.s 9.  monticolze  Hopk.,  page  105. 

Length  4.5  to  7*mm.;  black;  elytral  stria-  distinctly  impressed,  punctures  dis- 
tinct and  coarse.  Black  Hills,  South  Dakota,  southward  through  Colorado 
and  southern  rtah,  into  New  Mexico  and  Arizona,  in  Pinus  and  Picea. 

10.  ponderosae  Hopk.,  page  109. 
Pronotum  with  small  shallow  punctures. 

Length  (i  to  S  mm. ;  black;  punctures  of  elytral  striae  distinct  throughout;  pronotum 
distinctly  shining.  Yosemite  National  Park,  California,  in  Pinus  jeffreyl  and 
/'.  pnnderosa 11.  je/reyi  n.  sp.,  page  114. 

DIVISION  II. 

it  usually  with  posterior  impression;  pronotum  with  large  and  small  punctures 

intermixed Subdivision  C,  pages  71, 117. 

it  without  posterior  impression;  pronotum  with  regular  punctures. 

Subdivision  D,  pages  72, 146. 
SUBDIVISION  C; 

tral  declivity  with  striae  deeply  impressed;  epistomal  process  narrow,  flat,  with 
lateral  sections  nearly  parallel;  pronotum  with  punctures  moderately  regular, 

and  with  long  hairs  on  dorsal  and  lateral  areas Section  a3,  page  71. 

il  declivity  with  striae  not  deeply  impressed;  epistomal  process  broad,  concave, 
and  the  lateral  sections  oblique;  punctures  of  pronotum  distinctly  irregular. 

Section  a4,  page  71. 
Section  aS. 

turn  with  coarse  punctures. 

Length  3.5  to  5  mm.;  reddish  to  brown;  pronotum  with  short  dorsal  and  lateral 
hairs;  apex  of  epistomal  process  not  extending  beyond  the  anterior  frontal 
margin.  New  Brunswick  to  Michigan  and  West  Virginia,  in  Larix. 

12.  simplex  Lee.,  page  117. 
Pronotum  with  fine,  shallow  punctures. 

Length  4  to  7  mm.;  reddish  to  dark  brown;  pronotum  shining,  with  long  dorsal 
and  lateral  hairs;  apex  of  epistomal  process  usually  extending  beyond  the 
anterior  margin  of  epistoma.  British  Columbia  southward  to  Texas,  westward 
to  California,  in  Pseudotsuga  and  Larix 13.  pseudotsugx  Hopk.,  page  121. 

Section  a4. 

Posterior  half  of  proepisternal  area  not  distinctly  punctured.  Subsection  b3,-page  71. 
Posterior  half  of  proepisternal  area  distinctly  punctured Subsection  b4,  page  72. 

Subsection  b3. 

Length  4.7  to  6  mm.;  body  stout;  reddish  to  black;  elytral  striae  quite  distinctly  im- 
proved toward  sides,  with  punctures  coarse  and  distinct;  interspaces  convex; 
rugosities  acute,  rather  closely  placed,  irregular.  New  Brunswick,  through 
l  anada,  New  England,  and  Michigan,  in  Picea. . .  14.  piceaperda  Hopk.,  page  126. 

Length  ">  to  7  mm.;  reddish  to  black,  shining;  punctures  of  prothorax  and  elytra 
coarser;  striae  of  lateral  area  not  distinctly  impressed,  the  interspaces  scarcely 
convex  or  rugose.  Idaho  and  Black  Hills,  South  Dakota,  to  New  Mexico  and 
westward  to  California,  in  Picea 15.  engelmanni  n.  sp.,  page  130. 


72  THE  SCOLYTID  BEETLES. 

Length  6  mm.;  elytra  reddish;  pronotum  darker;  elytral  striae  moderately  im- 
pressed, punctures  of  striae  of  dorsal  area  small,  obscure,  and  those  of  the  lateral 
area  moderately  coarse;  interspaces  flat,  with  rugosities  moderately  coarse,  obtuse, 
and  rather  densely  placed;  pronotum  with  punctures  more  regular  in  size  than 
usual.  Alaska 16.  borealis  n.  sp.,  page  133. 

Length  6  to  7  mm. ;  black;  elytral  striae  but  faintly  impressed;  punctures  rather  coarse; 
interspaces  flat;  rugosities  moderately  coarse,  not  dense,  acute  toward  vertex; 
pronotum  with  fine  punctures,  moderately  dense,  coarser  toward  sides.  Pacific 
coast,  Oregon  to  Sitjca,  in  Picea  sitchensis 17.  obesus  (Mann.),  page  135. 

Subsection  b4. 

Striae  of  declivity  with  fine  punctures Series  c3,  page  72. 

Striae  of  declivity  with  coarse  punctures Series  c4,  page  72. 

Series  c3. 

Length  5  to  7.3  mm.;  elytra  red;  pronotum  brown  to  black;  body  rather  stout;  elytral 
striae  scarcely  impressed,  except  on  dorsal  area;  strial  punctures  moderately 
coarse;  rugosities  of  interspaces  moderately  coarse,  acute,  not  dense;  pronotal 
punctures  coarse,  deep,  moderately  dense;  elytral  declivity  with  interspaces 
moderately  punctured.  Lake  Superior,  in  Pinus  strobus. 

18.  rufipennis  (Kirby),  page  138. 

Length  5.4  to  6.5mm.;  elytra  dark  reddish;  pronotum  dark;  body  somewhat  slender, 
as  compared  with  species  18;  elytral  striae  moderately  impressed;  punctures 
coarse,  shallow;  pronotal  punctures  coarse,  not  distinctly  irregular  and  mod- 
erately dense;  elytral  declivity  with  interspaces  finely  densely  produced. 
Yellowstone  National  Park  and  Keystone,  Wyoming;  Alberta,  and  British  Colum- 
bia, in  Pinus 19.  murrayanse,  n.  sp.,  page  140. 

Series  c4- 

Length  6.5  mm.;  brownish;  elytral  striae  impressed;  punctures  coarse,  interspaces 
narrow  and  moderately  coarse,  acute,  rugosities  coarser  toward  the  suture. 

New  York  to  West  Virginia,  in  Picea 20.  punctatas  Lee.,  page  142. 

Length  7  to  8  mm.;  brownish;  elytral  striae  not  impressed  on  dorsal  or  lateral  areas, 
punctures  moderately  coarse,  shallow;  interspaces  broad,  flat,  shining;  rugosities 
small,  obtuse,  sparse.  Europe,  etc.,  in  Picea,  Larix,?  and  Abies'? 

21.  micans  (Kug.),  page  143. 
SUBDIVISION  D. 

Pronotum  somewhat  elongate,  slightly  narrower  than  elytra,  moderately  constricted 
toward  head,  median  and  posterior  dorsal  areas  without  long  hairs,  but  hairs  pres- 
ent on  anterior  and  lateral  areas;  head  broad,  epistomal  process  usually  broad, 
concave,  with  sides  strongly  oblique;  elytral  rugosities  variable,  usually  coarse. 
Body  black. 

Length  5  to  8  mm.;  black;  epistomal  process  moderately  broad,  with  apical 
angles  usually  tuberculate;  pronotal  punctures  very  coarse,  regular,  moderately 
dense,  scarcely  decreasing  in  size  toward  base;  elytra  without  long  hairs  toward 
base.  Long  Island,  New  York,  south  to  Florida,  west  to  West  Virginia  and 

Texas,  in  Pinus 22.  terebrans  (Oliv.),  page  147. 

Body  reddish. 

Length  5.7  to  9  mm.;  reddish,  never  black;  epistomal  process  broad,  with  apical 
angles  obtuse,  never  tuberculate;  pronotum  with  punctures  smaller  and  denser 
toward  base;  elytra  with  long  hairs  toward  base.  Eastern  United  States  and 
Canada,  north  of  mountains  of  North  Carolina,  westward  to  Pacific  coast,  south 
from  British  Columbia  into  Mexico,  in  Pinus  and  Picea. 

23.  valens  Lee.,  page  151. 


THE   GENUS  DENDROCTONUS.  73 

SYNOPSIS   OF   SECONDARY   SEXUAL  CHARACTERS. 

DIVISION   1. 

F<-ni'jli's:  Anterior  pronotal  area  with  transverse  ridge Subdivision  A. 

V.s-.  Anterior  pronotal  area  without  transverse  ridge Subdivision  B. 

SUBDIVISION  A. 

Females:   With  transverse  ridge  across  the  anterior  area;  elytral  declivity  slightly 

smoother,  more  shining,  and  less  rugose Species  1  to  8,  inclusive. 

MuL:*:    \Vithout  transverse  ridge  across  the  anterior  area,  but  with  broad  impression. 

Species  1  to  8,  inclusive. 
SUBDIVISION  B. 

Females:  Elytral  declivity  with  interspaces  more  shining,  rugosities  less  prominent. 

Species  9  to  11,  inclusive. 
Males:  Elytral  declivity  with  interspaces  more  opaque,  rugosities  more  prominent. 

Species  9  to  11,  incluoive. 
DIVISION  II. 

Elytral  declivity  with  distinct  sexual  characters  in  both  sexes Subdivision  C. 

Elytral  declivity  without  distinct  sexual  characters  in  either  sex Subdivision  D. 

SUBDIVISION  C. 

Females:  Interspaces    of    elytral    declivity    rugose.     Males:  Interspaces    of    elytral 

declivity  smooth. 
Striae  of  elytral  declivity  impressed;  interspaces  convex  in  both  sexes. 

Section  a3,  Species  12  and  13. 
Striae  of  elytral  declivity  not  impressed;  interspaces  flat Section  a4. 

Section  a4. 

lies:  Striae  of  elytral  declivity  slightly  impressed;  interspaces  subconvex. 

Species  14  to  21,  inclusive. 
Striae  of  elytral  declivity  not  impressed;  interspaces  flat. 

Species  14  to  17,  inclusive. 

?:  Striae  of  elytral   declivity  slightly  impressed;  interspaces  subconvex,   but 
smoother  than  in  female Species  18  to  21,  inclusive. 

SUBDIVISION  D. 

Females:  Head  with  front  moderately  broad;  mandibles  shining,  moderately  stout; 

antennal  club  broader Species  22  and  23. 

Males:  Head  with  front  broad;  mandibles  opaque,  stout;  antennal  club  narrow,  more 

elongate  and  less  compressed Species  22  and  23. 

SYNOPSIS  OF  PUPAL  CHARACTERS. 

Vertex  of  head  distinctly  to  faintly  grooved,  and  with  two  small  or  prominent  frontal 
spines  on  or  toward  the  vertex  each  side  of  groove Division  I. 

Vertex  of  head  faintly  impressed,  flat  or  convex,  and  with  two  small,  widely  separated 
frontal  granules  toward  vertex Division  II. 

DIVISION  I. 

Frontal  spines  small;  elytral  pads  smooth;  abdominal  tergites  2  to  6  with  or  without 
small  pleural  spines Subdivision  A. 

Frontal  spines  large,  prominent;  elytral  pads  rugose;  abdominal  tergites  2  to  6  with 
prominent  pleural  spines Subdivision  B. 


74  THE  SCOLYTID  BEETLES. 

SUBDIVISION  A. 

Anterior  and  middle  femora  smooth;  abdominal  tergites  3  to  6  with  small  pleural  spines; 

1  and  2  without  distinct  dorsal  and  lateral  spines.   Section  a  I,  Species  1,  2,  and  3. 

Anterior  and  middle  femora  with  small  apical  spines Section  a2. 

Section  a> . 

Abdominal  tergites  2  to  6  without  distinct  pleural  spines;  7  and  8  with  small  gran- 
ules   Species  4. 

Abdominal  tergites  2  to  6  with  small  pleural  spines  of  equal  size;  7  and  8  with  small 

granules .*. .  -  -  Species  5. 

Abdominal  tergites  1  to  6  with  small  pleural  spines,  increasing  in  size;  7  and  8  smooth. 

Species  8. 
SUBDIVISION  B. 

Apex  of  anterior  and  middle  femora  with  two  spines Species  9. 

Apex  of  anterior  and  middle  femora  with  one  spine;  abdominal  spines  and  elytral 

rugosities  coarser  than  in  species  9 Species  10. 

Apex  of  anterior  and  middle  femora  with  two  spines;  abdominal  spines  apparently  less 

prominent  than  in  species  9  and  10. Species  11. 

DIVISION  II. 

Vertex  of  head  fattened  or  faintly  impressed ;  apex  of  front  and  middle  femora  smooth 
or  with  minute  granule;  abdominal  tergites  with  pleural  and  dorsal  spines  moder- 
ately prominent '. Subdivision  C. 

Vertex  of  head  convex;  front  and  middle  femora  each  with  a  minute  pilated,  subapical 
granule;  abdominal  tergites  with  less  distinct  pleural  and  dorsal  spines. 

Subdivision  D. 
SUBDIVISION  C. 

Tergal  spines  of  abdomen  with  pale  or  white  tips;  segment  7  smooth Section  a3. 

Tergal  spines  of  abdomen  with  pale,  dark,  or  black  tips;  segment  7  with  a  few  setigerous 
granules Section  a4 . 

Section  a3. 

Anterior  and  middle  femora  with  minute  apical  spines;  abdominal  tergites  2  to  6  with 
stout,  prominent  pleural  spines;  3  to  6  with  prominent  dorsal  spines.  Species  12. 

Anterior  and  middle  femora  without  apical  spines;  abdominal  tergites  2  to  6  with  mod- 
erately stout  pleural  spines,  and  3  to  6  with  small  dorsal  ones Species  13. 

Section  a4. 

Vertex  of  head  moderately  impressed;  anterior  and  middle  femora  without  apical  spines; 

abdominal  tergites  2  to  6  with  very  small  pleural  spines;  4  to  6  with  small  dorsal 

spines,  all  with  pale  tips Species  14. 

Vertex  of  head  distinctly  impressed;  abdominal  tergites  2  to  6  with  distinct  pleural 

spines,  and  3  to  6  with  distinct  dorsal  ones Species  15. 

Abdominal  tergites  2  to  6  with  very  small  pleural,  lateral,  and  dorsal  spines,  all  with 

dark  tips Species  17. 

SUBDIVISION  D. 

Abdominal  tergites  1  to  6  with  moderately  small  pleural  spines,  2  to  6  with  small  dorsal 

and  lateral  ones,  all  with  pale  tips Species  22. 

Same  as  preceding,  except  spines  have  darker  to  black  tips Species  23. 


THE   GENUS  DENDROCTON VS.  75 

SYNOPSIS  OF  LARVAL  CHARACTERS. 

Abdominal  termites  S  and  !>  trillion f  dorsal  plates Division  1. 

Abdimiiiml  termite-  x  ;md  !»  with  dorsal  plates,  except  in  section  n:i Division  II. 

DIVISION  I. 

Front  with  or  without  median  convexity Subdivision  A. 

Front  //•///;  trnn*irrxc  elevation  slightly  more  prominent  toward  the  sutures. 

Subdivision  B. 
SUBDIVISION  A. 

Front  mthout.  median  convexity Section  al. 

Front  with  median  convexity Section  a2. 

Section  al. 

Clypeus  with  apex  xulmntti-lii  emarginate Species  1. 

( 'lypeus  with  apex  broadly  emarginate Species  2. 

Section  a.'. 

Prot horacic  lobes  mthout  foot  calli Subsection  bl. 

Prothoracic  lobes  with  distinct  foot  calli Subsection  b2. 

Subsection  b1 . 

Front  smooth,  with  shining  convexity;  clypeus  with  apex  broadly  emarginate. 

Species  3. 
Subsection  b2. 

Front  smooth,  with  median  smooth  convexity;  clypeus  with  apex  deeply  emargi- 
nate   Species  4. 

Front  with  anterior  third  transversely  rugose  and  with  transverse  median  convexity, 
produced  toward  apex;  clypeus  with  apex  broadly  emarginate Species  5. 

Front  with  broad  convexity;  clypeus  with  apex  truncated Species  8. 

SUBDIVISION  B. 

Front  of  head  with  posterior  apex  subacute;  frontal  elevation  moderately  stout  in  the 
middle;  clypeus  with  faint  median  tubercle  toward  the  base Species  9. 

Front  of  head  with  posterior  apex  subobtuse;  frontal  elevation  stout  slightly  posterior 
to  the  middle;  clypeus  with  a  faint  median  groove  and  elevation  toward  base. 

Species  10. 

Front  of  head  with  posterior  apex  subacute;  frontal  elevation  narrow,  situated  in  the 
middle,  not  more  distinctly  elevated  toward  suture;  clypeus  with  faint  median 
groove,  without  elevation J Species  11. 

DIVISION  II. 

Abdominal  tergites  8  and  9  without  dorsal  plate,  or  with  unarmed  plates. 

Subdivision  C. 
Abdominal  tergites  8  and  9  with  armed  plates Subdivision  D. 

SUBDIVISION  C. 

Abdominal  tergites  8  and  9  without  dorsal  plates Section  a3. 

Abdominal  tergites  8  and  9  with  dorsal  plates,  excepting  micans,  in  which  8  is  un- 
armed.. .  Section  a4. 


76  THK    SCOLYTID    BEETLES. 

Section  o-i. 

Front,  wit.h  hi  distinct  transverse  elevation;  clypeus  with  distinct  median  impression. 

Species  12. 
Front  with  distinct  transverse  elevation;  clypeus  with  median  impressed  line. 

Species  13. 
Section  0,4. 

Abdominal  tergites  8  and  9  with  rugose  but  unarmed  plates;  front  with  faint  trans- 
verse elevation  anterior  to  middle;  clypeus  with  median  groove Species  14. 

Frontal  elevation  near  the  middle Species  15. 

Frontal  elevation  distinctly  anterior  to  middle Species  16. 

Front  with  lateral  impressions  toward  the  anterior  angles,  and  frontal  elevation  ante- 
.  rior  to  middle Species  19. 

Abdominal  tergite  9  with  dorsal  plate;  frontal  elevation  anterior  to  middle;  clypeus 
with  median  groove Species  21. 

SUBDIVISION  D. 

Abdominal  tergites  8  and  9  each  with  dorsal  plate  and  armed  with  three  permanent 
teeth;  front  of  head  without  elevation;  clypeus  with  faint  median  groove. 

Species  22  and  23. 

SYNOPSIS  OF  GALLERY  CHARACTERS. 

Egg  galleries  winding  to  straight;  eggs  isolated  or  in  approximate  groups,  but  never  in 

masses;  larval  mines  exposed  or  concealed  in  inner  bark Division  I. 

Egg  galleries  longitudinal,  straight  to  slightly  winding;  eggs  in  groups  or  masses;  larval 
mines  and  pupal  cells  exposed  in  inner  bark Division  1 1 . 

DIVISION  I. 

Pupal  cells  in  outer  bark;  eggs  isolated,  never  in  groups;  egg  galleries  winding;  larval 
mines  short,  narrow  to  broad,  exposed  or  concealed Subdivision  A. 

Pupal  cells  in  inner  bark;  eggs  in  approximate  groups;  egg  galleries  slightly  winding 
to  straight;  larval  mines  short,  broad,  always  exposed Subdivision  B. 

;  SUBDIVISION  A. 

Larval  mines  concealed  in  inner  bark Section  al. 

Larval  mines  exposed  or  concealed Section  a2. 

Section  al. 

Egg  galleries  subtransverse,  winding Species  1. 

Egg  galleries  distinctly  transverse Species  2. 

Section  a2. 
Larval  mines  exposed. 

Egg  galleries  longitudinal,  winding Species  3. 

Egg  galleries  sublongitudinal,  winding Species  4. 

Larval  mines  concealed. 

Egg  galleries  evidently  transverse,  or  subtransverse,  winding,  with  concealed 

larval  mines Species  5. 

Egg  galleries  subtransverse,  winding Species  6. 

Egg  galleries  longitudinal,  winding,  with  transverse  branches. .  Species  7  and  8. 

SUBDIVISION  B. 

Egg  galleries  winding  to  straight Species  9. 

Egg  galleries  usually  straight Species  10  and  11. 


THE   GENUS  DENDKOCTONUS.  77 

DIVISION    II. 

Larval  mines  separate,  especially  beyond  the  middle  ................  Subdivision  (  '. 

Larval  mines  con  //>///  mis,  forming  broad  larval  chamber  ..............   Subdivision  D. 

SUBDIVISION  ('. 

Egg  galleries  slightly'winding  to  straight  eggs  in  groups,  but  larval  mines  separate 
from  the  beginning  ...............................................  Section  a3. 

Egg  galleries  broad,  nearly  straight;  eggs  in  small  to  large  groups,  the  larval  mines 
usually  contiguous  toward  the  egg  gallery  ..........................  Section  a4. 


Larval  mines  normally  short  and  broad  .................................  Species  12. 

Larval  mines  normally  long  ........................  .  ...................  Species  13. 

Section  0.4. 

Subsection  b3. 

Larval  mines  separated  beyond  the  middle  ..................   Species  14,  15,  and  16. 

Subsection  b4. 

Larval  mines  usually  not  separated  beyond  the  middle,  but  forming  a  common  chamber. 

Species  19  to  21. 
SUBDIVISION  D. 

Egg  galleries  broad  to  very  broad,  short  to  very  long,  straight  to  winding;  larval  mines 
forming  a  large  common  chamber  ............................  Species  22  and  23. 

TABLE  OF  DISTRIBUTION^ 
America,  north  of  Guatemala,  and  in  northern  Europe  ...........  .  .......  The  genus. 

DIVISION  I. 
SUBDIVISION  A. 

North  American  continent,  in  South  Atlantic  and  Gulf  States  and  Southwestern 
States,  southward  to  Guatemala  and  northward  in  Sierra  Nevada  and  Cascade 
Mountains  to  British  Columbia  ............................  Sections  al  and  a2. 

Sectional. 

\\f<l  of  western  Montana  and  southwestern  Idaho,  and  southward  to  Santa  Barbara 
County,  California  ........................  .  ................  Species  1,  page  81. 

South  of  southern  Colorado  and  Utah,  into  Texas  and  Mexico,  and  westward  into 
southern  California,  and  possibly  in  the  Coast  Range  and  northward  along  the 
forested  foothills  into  northern  California  .....................  Species  2,  page  85. 

Section  a2. 

Southern  Colorado  and  Utah,  southward  into  Mexico  .............  Species  3,  page  87. 

At  laiitic  and  Gulf  States,  south  westward  into  Texas  .............  Species  4,  page  90. 

<  '(Mitral  to  southern  Arizona  ..................................  Species  5,  page  95. 

Southern  Mexico  ...................................  Species  6  and  7,  pages  97,  99. 

Central  Colorado  and  southern  Utah,  southward  to  southern  Arizona,  and  New  Mexico. 

Species  8,  page  101. 

a  For  exact  and  probable  distribution  see  maps  under  description  of  each  species. 


78  THE  SCOLYTID  BEETLES. 

SUBDIVISION  B. 

West  of  western  Montana  and  southwestern  Idaho,  south  through  the  Sierra  Nevada 
Mountains  of  California Species  9,  page  105. 

Western  South  Dakota  and  southern  Wyoming,  southward  through  Utah,  Colorado, 
to  southern  Arizona  and  New  Mexico Species  10,  page  109. 

Northern  California,  southward  in  Sierra  Nevada,  into  San  Bernardino  County,  Cali- 
fornia   Species  11,  page  114. 

DIVISION  II. 
SUBDIVISION  C. 

Maine  to  western  Michigan,  southward  into  northwestern  West  Virginia. 

Species  12,  page  117. 

Northern  Idaho  and  Montana,  south  to  southern  Arizona  and  New  Mexico,  and  north- 
ern Washington,  south  into  Santa  Barbara  County,  California.  Species  13,  page  121 . 

Section  0,4. 

Maine  to  northeastern  Minnesota,  southward  to  central  Pennsylvania. 

Species  14,  page  126. 
Northern  Idaho,  east  to  western  South  Dakota,  southward  to  southern  Arizona  and 

New  Mexico Species  15,  page  130. 

Alaska Species  16,  page  133. 

Alaska?,  along  the  coast  to  northwestern  California Species  17,  page  135. 

Lake  Superior  region Species  18,  page  138. 

Western  Montana  southeast  to  central  Colorado Species  19,  page  140. 

Higher  mountains  of  New  York,  Pennsylvania,  and  West  Virginia.  Species  20,  page  142. 
Central  Europe  to  Denmark,  Russia,  and  eastward  into  Siberia.  Species  21,  page  143. 

SUBDIVISION  D. 

Atlpntic  States  south  of  Massachusetts,  to  Tampa,  Florida,  westward  to  western  West 
Virginia  and  Texas Species  22,  page  147. 

Mountains  and  foothills  of  North  Carolina,  northward  into  Maine  and  northwestern 
Washington,  southward  into  Guatemala Species  23,  page  151 . 

Guatemala Species  24,  page  157 . 

TABLE  SHOWING  RELATION  OF  SPECIES  TO  HOST  TREES. 

DIVISION  I. 

Section  al . 

Species    1.  Pinus  lambertiana,  ponderosa. 

Species    2.  Pinus  ponderosa  var.  scopulorum,  edulis;  Pseudotsuga  faxifolia. 

Section  at. 

Species    3.  Pinus  scopulorum. 
Species    4.  Pinus  strobus,  txda,  rigida,  rirginiana,  pungens,  echinata,  glabra,  palustris; 

Picea  rubens  and  excelsa. 
Species    5.  Pinus  scopulorum. 

Species    6.  Pinus  teocotlt,  lejophilla,  and  ayacahuite^ 
Species    7.  Same  as  6. 
Species    8.  Pinus  arizonica,  scopulorum.  and  chihuahuana. 

SUBDIVISION  B. 

Species    9.  Pinus  monticola,   lambertiana,  ponderosa,  murrayana;  Picea  engelmanm. 
Species  10.  Pinus  flexilis  and  strobiformis. 
Species  11.  Pinus  lambertiana  and  ponderosa. 


THE   GENUS  DBNDBOCTONUS. 


79 


DIVISION  II. 

Section  a.:. 

Species  12.  Larix  laricina. 

Species  13.  Larix  occidental  ix:  /'xci/'/otx/n/u  in  rifolia  and  macrocarpa. 

Species  14.  Picea  mariana,  rubens,  canadensis. 

Species  lo.  I'icdi  rdtLd'fciixix  and  engelma/ 

ies  Mi.  /Vmz  canadcnsi*. 

Species  17.  Picea  sitchensis. 

Subsection  1)4. 

Species  18.  Pinus  strobus. 

Species  19.  Pinus  murray<n«i;  I 'inn  <  tn/clmanni. 

Species  20.  Picea  rubens. 

Species  21.  Pinus,  Picea,  Abies?,  Lari.i . 

SUBDIVISION  D. 

Species  ~2'2.  Pinus  strobus,  tseda,  rigida,  serotina,  echinata,  palustris. 

Species  i':).   Pin-us  strobus,  monticola,  lambertiana,  strobiformis,  ponderosa,  scopuloruin, 

jeffreyi,  chihuahuana,  murrayana,  radiata,  rigida,  virginiana;  Larix  luricina; 

Picea  rubens,  canadensis,  excelsa. 


TABLE  OF  HOST  TREES. 


Dendroctonus  spe- 
cies number. 

Pinus  strobus 4, 18,  22,  23. 

monticola 9,  23. 

lambertiana 1,9,11,23. 

flexilis 10. 

strobiformis 10,23. 

edulis 2,23. 

arizonica 8,  23. 

ponderosa* 1,  9, 11,  23. 

scopulorum 2, 3,  5,  8, 10, 23. 

je/reyi 11,23. 

chihuahuana 3,  8,  23. 

murrayana 9, 10, 19,  23. 

radiata 23. 

tseda 4,  22. 

/•/>/;</« -4,22,2:;. 

serotina 22. 

virginiana 4,  23. 

pungens 4. 


Dendroctonus  spe- 
cies number. 


Pinus  echinata 4,  22. 

glabra 4. 

palustris 4,  22. 

sylvestris 23. 

teocotl 6,7. 

kjophilla 6,  7. 

ayacahuite 6,7. 

Larix  laricina 12,  23. 

occidentalis 13. 

Picea  mariana 14. 

rubens 4,14,20,22,23. 

canadensis 14,15,16,23. 

engelmanni 9, 10, 15, 19. 

sitchensis 17. 

excelsa 4,23. 

Pseudotsuga  taxifolia 2, 13. 

macrocarpa..  13. 


REVISION  AND   SYSTEMATIC   NOTES,   WITH  DESCRIPTIONS   OF 

NEW  SPECIES. 

DISTINCTIVE   GENERIC  CHARACTERS. 

Adult  (figs.  1,  2,  3). — Antennal  funiculus  5-jointed;  club  broad, 
thickened  at  base,  compressed  toward  apex,  and  usually  with  4  dis- 
tinct segments,  the  sutures  curved  or  nearly  straight;  tarsi  with  joint 
3  bilobed;  tibia  with  inner  angle  produced  and  armed  with  a  single 
tooth;  outer  angle  oblique  and  armed  with  3  or  more  stout  teeth; 
distinct  dorsal  impression  toward  apex  for  the  retractile  tarsus. 


80  THE  SCOLYTID  BEETLES. 

Anterior  ct>xae  approximate  or  subcontiguous.     Abdominal  sternites 
with  ends  of  sutures  4,  5,  and  6  strongly  recurved.     Body  cylindrical, 
subelongate  to  stout,  ranging  in  color  from  reddish  and  brown  to 
deep  black.     Head  prominent  and  large,  with  distinct  epistomal  proc- 
ess   at    anterior    margin   of  front.     Eyes   transversely  placed   andj 
oblong-oval  to  oblong-ovate.     Antennal  insertion  in  front  of  ventral ; 
end  of  eye.     Pronotum  with  sides  nearly  parallel  to  narrowed  and( 
constricted  toward  head,  one-fourth  to  one-third  broader  than  long,  j 
Elytra  with  base  elevated  and  rugose,  remaining  surface  rugose,  with ! 
punctured  striae  and  the  declivity  convex  to  subconvex. 

Pupa  (figs.  37,  38) . — The  pupa  is  of  the  general  size  of  the  adult,  and  j 
is  distinguished  by  its  broad  prominent  head,  and  the  form  of  the  pro- 
thorax.    The  sculpture  and  armature  vary  with  the  age  of  the  specimen. 
In  the  preimaginal  stage  the  granules  and  spines  become  more  obscure. 

Larva  (text  fig.  39;  PL  VIII). — The  body  of  a  matured  larva 
of  a  given  species  is  somewhat  longer  than  the  adult  or  pupa,  and 
is  cylindrical,  deeply  wrinkled,  legless,  and  with  a  few  long  hairs  on 
each  segment,  becoming  longer  on  the  posterior  ones.  The  head 
is  moderately  large,  shining,  yellowish,  and  with  a  few  hairs  on  the 
scutellar  lobes.  Front  distinct;  antennae  present,  but  obscure;  eye 
spots  not  present.  The  thoracic  segments  are  larger  and  more  prom- 
inent in  some  species  than  in  others.  Abdominal  segments  1  to  9  are 
of  about  equal  width  and  length;  10  is  represented  by  the  anal  lobe. 

Egg. — Short,  oval  to  oblong-oval,  pearly  white  and  shining,  and 
apparently  without  sculpture  and  specific  characters,  except  in  rela- 
tive size,  corresponding  with  the  size  of  adult  representatives  of  the 
species. 

Galleries. — The  primary  or  egg  galleries  are  excavated  in  the  inner 
bark  and  sometimes  mark  or  groove  the  wood  and  vary  in  their  course 
in  the  bark  of  the  tree  from  transverse  and  winding  to  longitudinal 
and  straight,  and  normally  are  of  the  single  unbranched  type. 

Distribution  (PL  II). — Eastern  continent:  Central  and  northern 
Europe,  from  Denmark  into  Siberia.  Western  continent :  Guatemala, 
northward  through  the  United  States  into  Alaska  and  Labrador. 

Host  trees. — Pinus,  Picea,  Pseudotsuga,  Larix,  and  Abies,  the  latter 
rarely,  if  at  all. 

BIBLIOGRAPHY  AND  SYNONYMY  OF  GENUS. 

Erichson,  1836,  pp.  52-53,  original  description,  to  include!),  micans  (Kug.)  (type),  D. 
terebrans  (Oliv.)  (cotype),  Myelophilus  piniperda  (L.),  Myelophilus  minor  (Hartig),  and 
Carphobortis minimus  (Fab.).  Eichhoff,  1864,  pp.  26-27,  PI.  I,  figs.  5, 6, 7,  tibia,  maxilla, 
labium,  revised  description  to  include  the  single  European  species,  D.  micans  (Kug.). 
Lacordaire,  1866,  pp.  360-361,  revision  to  include  D.  micans  (Kug.)  and  D.  tercbrunx 
(Oliv. ) .  Zimmerman,  1868,  pp.  148-149,  revision  to  include  Carphoborus  bifurcus  Eich . , 
D.  terebrans  (Oliv.),  and  D.  frontalis  Zimm.  Le  Conte,  1868,  pp.  172-173,  revision  to 
include!),  terebrans  Lac.,  D.  obesus  (Mann.),  D.  rufipennis  (Kirby),  D.  punctatus  Lee., 


Tech.  Series  17    Part  I,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


PLATE  II. 


THE   GENUS   DENDROCTONUS.  81 

D.  simplex  Lee.,  D.  frontalis  Zimm.,  eliminating  Carphoborus  bifurcus  Eichh.  Eich- 
lioff.  1881,  pp.  125,  brief  revision,  including  D.  micans  (Kug.).  Le  Conte  and  Horn, 
1883,  p.  523,  in  synoptic  table.  Dietz,  1890,  pp.  27-28,  revision  and  synopsis  to 
include  D.  terebrans  (Oliv.),  D.  rufipennis XKirby),  D.  similis  Lee.,  D.  simplex  Lee., 
D.  <i pproximatus  n.  sp.,  and  D.  frontalis;  revised  description  of  species,  with  syn- 
onymy, figs.  1-6,  epistqmata  and  antennae.  Hopkins,  1894b,  p.  280,  author's  extra,  p.  7, 
sexual  characters  of  D.  terebrans  (Oliv.),  D.  frontalis  Zimm.  Blandford,  1897,  p.  143, 
synoptic  table.  Lovendal,  1308,  pp.  86-87,  PI.  II,  fig.  7,  antenna,  fig.  8,  tarsus. 
Hopkins,  1902a,  pp.  3-4,  secondary  sexual  characters,  statistics,  etc.  Hopkins,  1906b, 
pp.  143-147,  larval  mouthparts. 

DIVISION  I. 

The  distinctive  characters  common  to  the  species  of  the  first  division 
are  as  follows: 

Adult. — Prothorax  somewhat  elongate  and  as  broad  as  elytra; 
anterior  dorsal  half  of  elytra  without  long  erect  hairs. 

Pupa. — Vertex  of  head  distinctly  to  faintly  grooved,  and  with  two 
prominent  to  small  frontal  spines  or  granules  on  or  toward  the  vertex 
each  side  of  groove. 

Larva. — Abdominal  tergites  8  and  9  without  dorsal  plates. 

Galleries. — Egg  galleries  winding  to  straight;  the  eggs  isolated  or 
in  approximate  groups,  but  never  in  masses;  larval  mines  exposed 
or  concealed  in  inner  bark. 

SUBDIVISION  A. 

(Species  numbers  1  to  8,  inclusive.) 

The  distinctive  characters  common  to  the  species  of  the  first  sub- 
division are  as  follows : 

Adult. — Body  somewhat  slender;  prothorax  with  sides  but  slightly 
narrowed  and  not  constricted  toward  the  head;  elytra  with  second 
stria  of  declivity  straight;  second  interspace  not  distinctly  broader 
hi  middle: 

Sexes. — Female:  Pronotum  with  transverse  ridge  across  anterior 
area.  Male:  Pronotum  without  transverse  ridge,  but  usually  with 
anterior  area  broadly  impressed. 

Pupa. — Elytra  smooth;  vertex  of  head  faintly  grooved  and  with 
two  small,  widely  separated  frontal  tubercles. 

Larva. — Front  with  or  without  median  convexity. 

Galleries. — Egg  galleries  winding;  larval  mines  exposed  or  con- 
cealed. Pupal  cells  in  outer  bark;  eggs  isolated,  never  in  groups. 

1.     Dendroctonus  brevicomis  Le  Conte. 
(PI.  Ill,  fig.  l.) 

Adult. — Typical  female:  Length,  4.6  mm.;  light  brown.  Elytral 
declivity  without  long  hairs.  Head  with  front  convex,  slight  eleva- 
tions each  side  of  a  faint  median  groove.  Elytral  rugosities  fine, 
densely  placed;  striae  obscure  and  but  faintly  or  not  at  all  impressed. 

79980—09 7 


82 


THE   SCOLYTID   BEETLES. 


Pronotum  with  a  few  reclining  long  hairs  on  the  anterior  half,  remain- 
ing areas  with  very  few  and  stout  pubescence.  Secondary  sexual 
characters:  Pronotum  with  transverse  ridge  extending  across  the 
anterior  area  to  near  the  sternum.  Elytral  declivity  moderately 
smooth  and  shining;  interspaces  finely  and  densely  punctured;  striae 
fine,  with  punctures  scarcely  visible. 

Typical  female  labeled  "type  of  revision,"  name  label,  "Hopk. 
4/18/02,"  second  name  label,  "Hopk.  Jan  16/08,  Pinus  ponderosa, 
Hopkins,  collector,  3/24/99,  Grant's  Pass,  Or.,  9  ,  Hopk.  U.  S.  34." 


FIG.  44.—Dendroctonus  brevicomis:  Egg  galleries.    (Original.) 

Type  male  in  Le  Conte  collection,  labeled  "Cal.,"  examined  by» 
writer. 

Typical  male:  Length  4.6  mm.     Agrees  with  female,  except  in  tl 
more  prominent  frontal  tubercles  each  side  of  a  distinct  groove 
a  transverse  impression  instead  of  an  elevation  across  the  anteric 
area  of  the  pronotum,  and  the  elytral  declivity  slightly  less  shi] 

Typical   male   labeled  "type  of  drawing,"   name  label,   "Hop! 
1/16/08,  Pinus  ponderosa,  Hopkins,  collector,  3/24/99,  Grant's 
Or.,   $ ,  Hopk.  U.  S.  34." 


THE   GENUS   DENDROCTONUS. 


83 


Variations. — Length,  3  to  5  mm.;  color  light  brow^nish  to  nearly 
black;  punctures  of  pronotum  ranging  from  moderately  coarse  to 
very  fine,  elytral  striae  not  at  all  impressed  in  some  examples,  in 
others  the  impression  and  punctures  more  distinct,  but  never  as 
distinct  as  in  ttje  majority  of  D.  barberi.  The  elytral  rugosities 
also  vary  from  very  fine  to  moderately  coarse.  The  front  varies 
greatly,  from  convex  without  tubercles  to  deeply  grooved  and  with 
prominent  tubercles.  The  epistomal  process  varies  from  the  nor- 
mal concave  form  with  angles  elevated  and  lateral  margins  strongly 
oblique  to  flat  with  rounded  apex  and  lateral  margin  suboblique. 

.Distinctive  characters. — 
The  adults  of  this  species 
are  at  once  distinguished 
from  its  nearest  ally,  D. 
barberi,  by  the  finer  rugo- 
sities of  the  elytral  inter- 
spaces and  the  much  less 
distinctly  impressed  striae. 

Revisional  notes. — The  «-  J.i 
labeled  type  in  the  Le 
Conte  collection  agrees 
with  the  description,  ex- 
cept that  the  prothorax  is 
not  nearly  twice  as  broad 
as  long.  It  is  certainly 
distinct  from  D.  frontalis. 
The  specimens  in  the  Horn 
collection  under  D.  fron- 
talis that  evidently  repre- 
sent part  of  the  material 
on  which  Doctor  Dietz 
based  his  revision,  include 

one  specimen  of  D.  frontalis  labeled  with  red  disk,  one  speci- 
men of  D.  brevicomis  labeled  "Cal.,"  one  specimen  of  D.  barberi 
labeled  " Williams,  Ariz.  7.  28,"  one  specimen  of  D.  arizonicus(T) 
11  Williams,  Ariz.  7.  28,"  and  one  specimen  without  locality  label. 
One  specimen  was  also  received  from  Dietz,  under  D.  frontalis, 
labeled  "  Arizona,"  which  proved  to  be  D.  barberi.  In  1898  D.  brevi- 
>s  Lee.  was  not  represented  in  the  U.  S.  National  Museum.  There- 
fore it  appears  that  up  to  1899  there  were  only  two  specimens  of  the 
species  in  the  large  collections  of  the  country. 

Pupa. — In  addition  to  the  divisional  and  subdivisional  characters, 
the  pupae  range  in  length  about  the  same  as  adults ;  the  apices  of  the 
front  and  middle  femora  are  smooth;  abdominal  tergites  3,  4,  5,  and 


£ 


FIG.  45. — Dendroctonus  brevicomis:   Bark  showing,  o,  pupal 
cells;  6,  exit  burrows;  c,  pitch  tubes.    (From  Webb.) 


84 


THE   SCOLYTID   BEETLES. 


6  with  small  pleural  spines,  1  and  2  without  distinct  dorsal  and  lateral 
spines.  Pupal  type  labeled  "Hopk.  U.  S.  34." 

Larva  (PL  VIII,  fig.  1). — In  addition  to  the  divisional  and  subdivi- 
sional  characters  the  larvae  range  slightly  longer  than  the  pupse. 
Epistoma  distinctly  elevated.  Front  without  median  convexity; 
clypeus  with  apex  subacutely  emarginate;  thoracic  segments  with 
prominent  sternal  lobes;  the  sternellar  lobes  with  distinct  foot  calli; 
apex  of  abdomen  subtruncate.  Larval  type  labeled  "  Hopk.  U.  S.  25a." 

Galleries  (figs.  44,  45). — Egg  galleries  subtransversely  winding; 
eggs  isolated;  larvae  concealed  in  inner  bark;  pupal  cells  in  outer  bark. 

Distribution  (fig.  46). — (Hopk.  U.  S.)  California:  McCloud,  Badger, 
Chester, Wawona,  Sterling,  Summerdale,  Yosemite,  Ballard.  Montana,: 


FIG.  40. — Dendroctonus  brevicomis:  Distribution  map.    (Original.) 

Missoula.  Oregon:  Grants  Pass,  Joseph.  Washington:  Buckeye  (near 
Spokane),  Chelan.  Idaho:  Moscow,  Smiths  Ferry,  Centerville,  Stites, 
Kooskia  (Harris  Ridge),  Pioneer  (Grimes  Pass),  Garden  Valley, 
Placerville,  Cedar  Mountains,  Troy. 

Host  trees. — Pinus  ponderosa  and  P.  lamlertiana. 

Identified  specimens. — Le  Conte,  1;  Horn,  1;  Hopk.  U.  S.,  several 
hundred,  including  all  stages  and  work. 

BIBLIOGRAPHY  AND  SYNONYMY. 

Dendroctonus  brevicomis  Le  Conte,  1876,  p.  386,  original  description,  synopsis, 
localities.  Packard,  1887,  p.  177,  Le  Conte  quoted.  Packard,  1890,  p.  722, 
Le  Conte  quoted.  Hopkins,  1899a,  p.  395,  reference.  Hopkins,  1899b,  pp.  13, 
20,  26,  first  records  of  habits,  hosts,  etc.  Hopkins,  1901b,  p.  66,  habits,  galleries, 
etc.  Hopkins,  1902a,  p.  3,  name  restored.  Hopkins,  1902c,  p.  21,  note.  Hop- 


THE   GENUS   DENDROCTONUS.  85 

kins,  1903b,  p.  281,  mentioned.  Hopkins,  1904,  p.  18,  habits,  distribution,  etc. 
\\Vbb,  1906,  bulletin,  Pis.  II,  III,  figs.  7-12,  stages  and  vork  illustrated,  full 
account  of  habits,  life  history,  etc.  Hopkins,  1908,  pp.  162-163,  depredations. 

Dendroctonus  frontalis  (not  of  Zimm.)  Dietz,  1890,  p.  32  (in  part),  California. 

Dendroctomis  brevicornis  Dietz,  1890,  p.  32  (in  part),  California. 

2.     Dendroctonus  barberi  n.  sp. 

(PI.  Ill,  fig.  2.) 

Adult. — Type  of  species,  female:  Length,  4.5  mm.;  very  dark 
brown.  Elytra  and  elytral  declivity  without  long  hairs.  Head  with 
front  convex,  with  slight  elevation  each  side  of  a  faint  median  groove. 
Elytral  rugosities  moderately  coarse  and  dense;  striae  distinctly 
impressed.  Pronotum  with  a  few  long  hairs  on  the  anterior  half  of 

.e  lateral  area,  the  remaining  area  with  very  fine  and  short  pubes- 
.ce.  The  secondary  sexual  characters  are  the  same  as  in  the 
eding  species. 

Type  labeled  "Type   No.    7444,  U.S.N.M.,"  name   label,  uHopk. 

15/08,  9  ,  individual  /,  Barber  &  Schwarz,  Collectors],  Williams,  Ar., 
.6"  (  =  June7). 

Male  type:  Length,  4  mm.  Front  with  prominent  tubercles  each 
side  of  a  distinct  groove.  Pronotum  without  transverse  ridge  across 
the  anterior  area,  but  with  a  broad  transverse  impression.  The 
elytral  declivity  shining,  with  strial  punctures  distinct  and  interspaces 
slightly  more  rugose  than  in  the  female. 

Male  type  labeled  "  $  type,"  otherwise  same  as  female,  except  type 
number. 

Variations. — Length  2.5  to  4.7  mm.,  color  from  brownish  to  black. 
The  frontal  and  prothoracic  variations  are  similar  to  those  of  D. 
brevicomis.  The  elytra  vary  from  rugosities  moderately  coarse  and 
obtuse  to  distinctly  coarse  and  acute,  and  striae  from  moderately  to 
very  distinctly  impressed,  and  the  punctures  from  obscure  to  distinct. 

Distinctive  characters. — The  adults  of  D.  barberi  are  at  once  distin- 
guished from  the  next  species  by  the  absence  of  long  hairs  on  the  ely- 
tral declivity,  and  from  D.  brevicomis,  to  which  it  is  closely  allied,  by 
the  prevailing  coarser  rugosities  of  the  elytral  interspaces  and  the 
distinctly  impressed  striae.  Some  systematists  might  concede  these 
characters  of  no  more  than  subspecific  or  varietal  value,  but  it  must 
be  remembered  that  in  this  genus  there  is  a  close  general  resemblance 
of  allied  species  and  that  the  characters  which  in  other  genera  would 
be  of  special  value  in  specific  distinction  are  so  variable  and  incon- 
stant in  this  as  to  be  of  no  value.  Therefore  any  constant  or  prevail- 
ing character  of  distinction,  even  if  it  does  seem  insignificant,  is  of 
vastly  higher  value  than  would  otherwise  be  allowable,  especially 
when  it  is  supported  by  differences  in  physiological  characteristics. 


86  THE  SCOLYTID  BEETLES. 

Revisional  note. — This  species  is  not  represented  in  the  Le  Conte 
collection.  One  specimen  labeled  "Williams,  Ariz.,  7.28,  151,"  and 
one  without  label  found  in  the  Horn  collection,  both  under  D.frontalis, 
and  one  specimen  labeled  "Ariz.,"  received  from  Doctor  Dietz  under 
D.  frontalis,  all  belong  to  D.  barleri.  These  were  evidently  before 
Doctor  Dietz  when  he  prepared  his  revision  of  D.  frontalis,  ibid. 

Pupa. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  apex  of  the  front  and  middle  femora  is  smooth;  abdom- 
inal tergites  3  to  6  with  very  small  dorsal,  lateral,  and  pleural  spines; 
land  2  without  dorsal  or  lateral  spines;  3  to  6  with  minute  dorsal  and 
lateral  spines;  7  and  8  smooth,  and  9  with  small  pleural  spines.  Pupal 
type,  labeled  "Hopk.  U.  S.  5030"  (in  alcohol),  differs  from  pupa  of 
D.  Irevicomis  in  the  absence  of  lateral  spines  on  abdominal  tergites 
3  and  4;  but  these,  with  other  pupal  characters,  are  so  variable  that 


FIG.  47,-Dendroctonus  barberi:  Egg  galleries.    (Original.) 

not  much  reliance  can  be  placed  on  any  of  them  to  separate  closely 
allied  species. 

Larva. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  clypeus  has  the  apex  broadly  emarginate  instead  of 
subacutely  emarginate,  as  in  D.  Irevicomis.  It  also  differs  in  the 
more  rounded  apex  of  the  labrum  and  in  the  more  distinctly  rugose 
mandibles.  Larval  type  labeled  "Hopk.  U.  S.  No.  5129 "  (mounted 
and  alcoholic). 

Galleries  (fig.  47). — In  addition  to  the  divisional  and  subdivisional 
characters,  the  egg  galleries  are  usually  distinctly  transversely  wind- 
ing, thus  differing  from  D.  Irevicomis;  otherwise  there  is  little 
difference. 

^  Distribution  (fig.  48).— (Hopk.  U.  S.)  Arizona:  Williams,  Flagstaff, 
San  Francisco  Mountains,  Grand  Canyon,  Walnut  Canyon,  Dead  Man's 


tt,  Show  Low,  Santa  Catalina  Mountains.  New  Mexico:  Vermejo, 
ita  Fe,  Meeks,  Capitan  (Mountains),  Cloudcroft.  Texas:  Davis 
Mountains.  Colorado:  Fort  Garland  and  Monte  Vista.  Utah:  Esca- 
lante  and  Panguitch.  Additional  localities  from  other  collections. 
(II.  &  S.)  Chiricahua  Mountains,  Ariz. 

Host  trees. — Panus  ponderosa  var.  scopulorum  (very  common),  P. 
edulis  (rare),  and  Pseudotsuga  taxifolia  (rare,  probably  abnormal). 

Identified  specimens. — Horn  collection,  2;  Dietz,  1;  U.  S.  N.  M., 
H.  &  S.,  2,  B.  &  S.,  62;  Hopk.  U.  S.,  more  than  400,  including  all 
stages  and  work. 


THE   GENUS   DENDROCTONUS. 


87 


I 

I  

i   7* 

'•1 

1 

""\    { 
l__^ 

1  

*•—  -» 

\-J 

1 

.     N 

FIG.  48.—Dendroctonus  barberi:  Distribution  map.    (Original.) 
BIBLIOGRAPHY  AND  SYNONYMY. 


Dendroctonus  frontalis  (not  of  Zimm.)  Dietz,  1890,  p.  32  (in  part),  Arizona. 
Dendroctonus  arizonicus  Hopkins,  1902a,  p.  3  (in  part),  manuscript  name  only. 
Dendroctonus  n.  sp.  Hopkins,  1904,  pp.  42,  44,  habits,  host,  distribution,  etc. 
Dendroctonus  brevicomis  var.  barberi  Hopkins,  1906b,  p.  147,  PL  IV,  fig.  9,  anatomy 
of  larval  head,  manuscript  name. 

3.     Dendroctonus  convexifrons  n.  sp. 

(Pi.  m,  ng.  3.) 

Adult. — Type  of  species,  female:  Length,  6  mm.;  reddish-brown, 
shining.  Elytral  declivity  with  long  hairs.  Head  with  front  convex; 
without  median  frontal  groove  or  tubercles,  but  with  posterior  impres- 
sion. Elytral  rugosities  moderately  coarse,  but  not  densely  placed, 
except  toward  the  base ;  striae  faintly  impressed  and  with  rather  coarse, 
indistinct  punctures.  Pronotum  with  long,  erect  hairs  on  the  entire 


gg  THE  SCOLYTID  BEETLES. 

lateral  area,  the  remaining  area  with  short,  erect,  and  sparse  pubes- 
cence. Secondary  sexual  characters:  Pronotum  with  transverse 
ridge  across  the  anterior  area,  extending  to  the  sternum.  Elytral 
declivity  shining;  striae  very  slightly  impressed;  punctures  obscure; 
interspacial  granules  sparse  and  small,  but  distinct. 

Type  labeled  "Type  No.  7445  U.S.N.M.,"  name  label,  "Hopk. 
1/16/08,  Pinus  ponderosa,  Hopkins,  Coir.,  9/8/02,  Williams,  Ariz.,  9  , 
Hopk.  U.  S.  1109." 

Male  type :  Length,  5.6  mm.  Front  convex  and  with  f aint  anterior 
and  posterior  impressions,  but  without  frontal  groove  or  tubercles. 
Pronotum  without  transverse  elevation.  Elytral  declivity  less  shin- 
ing; striae  more  impressed,  with  more  distinct  punctures  and  the  inter- 
spacial granules  distinctly  coarser  than  hi  the  female. 

Male  type  labeled  "  $  type;"  otherwise  same  as  female,  except 
type  number. 

Variations. — The  length  varies  from  4  to  6  mm.,  with  the  average 
at  about  5.5  mm. ;  the  color  ranges  from  reddish  to  black,  with  red- 
dish-brown prevailing;  front  ranges  from  completely  convex  without 
median  impression  to  more  or  less  distinctly  impressed,  but  never 
with  frontal  tubercles.  The  punctures  of  the  pronotum  vary  as 
usual,  and  the  dorsal  area  ranges  from  the  absence  of  a  longitudinal 
median  space  or  line  to  a  distinct  elevated  line. 

Distinctive  characters. — The  adults  of  D.  convexifrons  are  at  once 
distinguished  from  D.  approximatus  by  the  more  slender  form  and 
shining  appearance,  and  the  prevailing  convex  front  in  both  sexes, 
which  latter  character  also  distinguishes  small  examples  of  the  species 
from  large  examples  of  D.  arizonicus.  The  long  hairs  on  the  elytral 
declivity  render  it  absolutely  distinct  from  D.  barberi,  to  which  it 
appears  to  be  more  closely  allied  on  account  of  pupal  characters. 

Revisional  notes. — This  species  is  not  represented  in  the  Le  Conte 
collection,  but  among  the  three  specimens  in  the  Horn  collection, 
under  D.  approximatus  Dietz,  there  was  one  labeled  "N.  M.,"  which 
certainly  must  be  referred  to  it. 

Pupa. — In  addition  to  the  divisional  and  subdivisional  characters, 
the  front  and  middle  femora  are  smooth  or  with  minute  apical 
granule;  abdominal  tergites  1  and  2  without  dorsal  spines  but  with 
one  or  two  lateral  granules;  2  to  6  with  very  small  lateral  spines,  and 
3  to  6  with  very  small  dorsal  and  lateral  spines,  becoming  more 
prominent  toward  the  sixth;  7  and  8  smooth  and  9  with  widely 
separated  caudal  spines.  Pupal  type  labeled  "Hopk.  U.  S.  No. 
5090." 

Larva. — In  addition  to  the  divisional  characters,  the  front  has  a 
median  smooth,  shining  convexity;  mandibles  distinctly  rugose  on 
lateral  area  toward  base;  labrum  with  apex  broadly  rounded  and 


THE   GENUS   DENDROCTONUS. 


89 


clypeus  with  apex  broadly  emarginate.  Sternellar  lobes  of  thoracic 
segment  without  foot  calli.  Larval  type  labeled  "Hopk.  U.  S.  No. 
5078." 

Galleries  (fig.  49). — Egg  galleries  longitudinally  winding;  eggs 
isolated;  larval  mines  exposed  in  inner  bark;  pupal  cells  in  outer  bark. 

The  galleries  of  this  species  are  at  once  distinguished  from  those 
of  D.  barberi  and  D.  approximate  by  the  exposed  larval  mines. 


FIG.  49.—Dendroctonus  convexifrons:  Egg  galleries  and  larval  mines.    (Original.) 

These  three  species  usually  infest  the  same  tree,  and  often  all  of 
their  galleries  are  represented  in  a  piece  of  bark. 

Distribution  (fig.  50). — (Hopk.  U.  S.)  Arizona:  Williams,  Flagstaff, 
Show  Low,  Paradise,  Santa  Catalina  Mountains,  and  Chiricahua 
Mountains.  Colorado:  Las  Animas  County,  La  Veta,  Fort  Garland, 
and  Monte  Vista.  New  Mexico:  Cloudcroft,  Meeks,  Capitan,  Fort 


90 


THE   SCOLYTID   BEETLES. 


Wingate  Military  Reservation,  Vermejo,  Lincoln  National  Forest, 
and  Sierra  Blanca  Mountains.      Utah:    Escalante,  La  Salle  National  i 
Forest,   and  Panguitch  Lake.     Additional  locality  from  other  collec-  ( 
tions:   (B.  &  S.)  Las  Vegas,  N.  Mex. 

Host    trees. — Pinus    ponder osa    var.    scopulorum    (very    common)  | 
and  P.  chihualiuana  (rare). 

Identified  specimens. — Hopk.    U.    S.,    more    than    100   specimens,  j 
including  all  stages  and  work;  Horn,  1  specimen  under  D.  approxi- 
matus,  labeled  "N.  M.";  U.S.N.M.,  B.  &  S.,  7  specimens,  Las  Vegas,  | 
N.  Mex.,  17-8,  No.  164,  and  Williams,  Ariz.,  5-6,  5-7,  and  5-10. 

BIBLIOGRAPHY. 

Dendroctonus  approximatus  Dietz,  1890,    p.   31  (in   part),  New  Mexico.     Schwarz,  ' 
1902,  p.  32  (in  part) . 


FIG.  50.— Dendroctonus  convexifrons:  Distribution  map.    (Original.) 

4.     Dendroctonus  frontalis  Zimmerman. 

/! 

(PI.  Ill,  fig.  4.) 

Adult. — Typical  female:  Length,  3.6  mm.;  reddish-brown.  Ely- 
tral  declivity  with  long  hairs.  Front  with  a  moderately  prominent 
tubercle  each  side  of  a  distinct  median  groove.  Elytral  striae  dis- 
tinctly punctured;  interspacial  rugosities  moderately  coarse,  obtuse, 
not  very  densely  placed,  and  not  very  distinctly  coarser  toward  the 
base  and  vertex.  Pronotum  with  a  few  long  hairs  on  the  anterior 
section  of  the  lateral  area.  Secondary  sexual  characters:  Pronotum 
with  transverse  ridge  across  the  anterior  area,  the  elytral  declivity 
shining  and  with  finery  granulate  interspaces,  the  striae  distinctly 
impressed,  but  the  punctures  obscure. 


THE  GENUS  DENDBOCTONUS. 


91 


Typical  female  labeled  "type  of  revision,  type  of  drawing/'  name 
label,  "Hopk.  4-18-02,  9 ,  II.  S.  58,  S.  C." 

Type  in  Le  Conte  collection  labeled  "Type  1,  D.  frontalis  (Fab.) 
Zimm.,"  red  disk  (=  Carolinas). 

Male  type:  Length,  3.5  mm.  Front  with  prominent  frontal 
tubercle  each  side  of  a  broad,  deep  frontal  groove.  Pronotum 
without  transverse  elevation  or  impression  across  the  anterior  area. 
Elytral  declivity  with  striae  more  impressed  and  the  interspacial 
granules  coarser  and  more  sparse  than  in  the  female. 


FIG.  51.— Dendroctonus  frontalis:  Egg  galleries  and  larval  mines,  a,  Entrance;  b,  entrance  burrow;  c,  egg 
gallery;  d,  normal  larval  mine;  e,  abnormal  larval  mine;/,  terminal;  g;  ventilating  burrows.    (Original.) 

Typical  male  labeled  with  name,  "Hopk.  1-16-08,  £,U.S.N.M. 
37,  sp.,  N.  C." 

Variations. — The  length  varies  from  2.5  to  4  mm.,  with  the  average 
at  about  3.2  mm.  The  color  ranges  from  light  brown  to  nearly  black; 
the  epistoma,  front,  prothoracic  punctures,  and  elytral  rugosities  vary 
as  usual.  The  anterior  area  of  the  pronotum,  which  is  glabrous  in 
the  typical  females  and  males,  usually  has  a  few  long  hairs. 

Distinctive  characters. — This  species  is  distinguished  from  D.  ari- 
zonicus,  its  nearest  ally,  by  its  smaller  size,  broader  pronotum,  with 
finer  punctures,  and  finer  and  less  acute  rugosities  of  the  elytra. 

Eevisional  notes. — The  type  series  in  the  Le  Conte  collection  is  repre- 
sented by  three  specimens — one  labeled  "Type  1,  D.  frontalis  (Fab.) 


92 


THE    SCOLYTID   BEETLES. 


Zimm.,"  red  disk  ( =  Carolinas) ,  which  should  stand  as  the  type,  and 
the  other  two  labeled  "Type  2"  and  "Type  3,"  same  locality. 
There  are  also  two  specimens,  one  labeled  "Specimen  4,  Lake  Supe- 
rior," and  the  other  labeled  "Specimen  5,  Va."  Both  of  these  agree 
with  the  West  Virginia  form.  In  addition,  there  are  three  specimens 
labeled  with  an  orange  disk  (  =  Georgia),  one  with  light  green  disk 
( =  Middle  States) ,  all  of  which  were  doubtless  before  Le  Conte  when 
he  drew  up  his  revised  description. 

The  series  in  the  Horn  collection,  which  was  evidently  before  Doc- 
tor Dietz  when  he  drew  up  his  revised  description,  includes  but  one 


• '  s^:^:- 


FIG.  52,—Dendrocto- 
nus  frontalis:  Ter- 
mination of  egg  gal- 
leries. (Original.) 


-  5£—Dendroctonus    fron-        FIG. 54. — Dendroctonus frontalis: 


tails:  Beginning  of  egg  galler- 
ies; a,  in  living  bark;  6,  in 
dying  bark;  c,  marked  on 
surface  of  wood  (white  area 
represents  normal  appear- 
ance of  wood  preserved  by 
resin).  (Original.) 


Bark  showing,  a,  pitch  tubes;  6, 
entrance  burrow;  c,  egg  gallery; 
d,  ventilating  burrow;  e,  pupal 
cells;  /,  exit  burrows;  g,  inner 
bark;  ft,  outer  bark.  (Original.) 


specimen  labeled  with  red  disk  (  =  Carolinas).  The  specimens  men- 
tioned, together  with  two  or  three  specimens  in  the  United  States 
National  Museum,  were  probably  all  that  were  in  the  larger  collec- 
tions of  the  country  up  to  1890. 

The  form  which  in  1891  and  1892  extended  northward  from  the 
normal  range  of  the  species  into  Virginia  and  West  Virginia  is  repre- 
sented in  the  revision  series  by  specimens  labeled  "Hopk.  W.  Va.  9 
individual  1"  and  "Hopk.  W.  Va.  $  individual  1."     The  West  Vir- 
ginia female  differs  from  the  typical  South  Carolina  female  in  a  more 


THE   GENUS   DENDROCTONUS. 


93 


•ugose  front,  prothorax  slightly  narrow  in  front,  with  a  few  short  and 
.ong  hairs  on  sides  and  the  punctures  of  anterior  dorsal  surface 
ijoarser  toward  base  and  fine  toward  anterior  margin ;  cly tral  rugosi- 
ties more  acute;  strial  punctures  coarser  and  more  distinct;  elytral 
[declivity  with  longer  and  more  numerous  hairs.  The  West  Virginia 
iale  differs  from  the  typical  North  Carolina  male  type  in  the  more 
(shining  front,  with  punctures  more  distinct,  while  the  pronotum  and 
plytra  show  the  corresponding  differences  mentioned  under  the 
female  individual  1.  At  one  time  it  seemed  to  the  writer  that  this 


lllEfi 

:-i  V* 


FIG.  55. — Dendroctonusfrontalis:  Old  egg  galleries 
in  living  tree,  with  surrounding  callus  of  new 
wood.  (Original.) 


FIG.  56.— Dendroctonusfrontalis:  Egg  gal- 
lery in  living  tree  marked  on  surface  of 
wood  six  years  before  block  was  cut 
from  tree,  a,  Mark  of  gallery  on  origi- 
nal surface;  b,  resinous  wood;  c,  surface 
scar  six  years  later;  d,  original  surface 
or  7-year-old  annual  layer  of  wood;  e, 
six  subsequent  annual  layers  of  wood 
formed  over  original  wound.  (Origi- 
nal.) 


inorthern  form  was  worthy  of  specific 

jdistinction,  and  the  manuscript  name 

:of  D.  pinicida  was  proposed  for  it,  but 

it  was  later  found  that  some  southern 

examples  showed  the  same,  and  even 

| greater,  variations  from  the  type.     Therefore,  since  the  species  had 

disappeared  from  its  northern  range,  it  was  decided  that  it  would  not 

be  advisable  to  recognize  it  as  specifically  distinct. 

Pupa. — In  addition  to  the  divisional  and  subdiyisional  characters 
the  apices  of  the  front  and  middle  femora  are  armed  with  small 
apical  spines  or  granules.  Abdominal  tergites  1  to  6  without  pleural 
spines;  1,  2,  and  3  without  distinct  dorsal  and  lateral  spines;  4  to  6 
with  a  pair  of  dorsal  spines  and  one  or  two  lateral  ones ;  7  and  8  with 


94 


THE   SCOLYTID   BEETLES. 


a  few  dorsal  granules,  and  9  with  medium-sized  caudal  spines.     Pupal 
type  labeled  "Hopk.  U.  S.  No.  2968." 

Larva, — In  addition  to  the  divisional  characters,  the  front  has  a 
distinct,  median,  smooth,  shining  convexity  produced  toward  vertex; 
clypeus  short,  broad,  with  apex  deeply  emarginate;  pro  thoracic  seg- 
ments very  large  and  sternellar  lobes  with  distinct  foot  calli.  Apex 
of  abdomen  truncate.  Larval  type  labeled  "  Hopk.  W.  Va.  No.  5976." 

The  frontal  convexity  is  more  rugose  in  some  specimens  than  in 
others. 

Galleries  (figs.  51-56). — Egg  galleries  sublongitudinal,  winding;  the 
eggs  isolated;  larval  mines  exposed;  pupal  cells  in  outer  bark. 

Distribution  (fig.  57). — (Hopk.  W.  Va.)  West  Virginia:  Hamp- 1 
shire,  Monongalia,  Hardy,  Pendleton,  Randolph,  Pocahontas,  Tucker,  ' 
Kanawha,  Raleigh,  Greenbrier,  and  Wood  counties.  Virginia:  Port 


FiG.57.—Dendroctonusfrontalis:  Distribution  map.    (Original.) 

Republic-.  Work  observed  in  southern  Pennsylvania,  Maryland,  and  j 
Virginia  (author).  (Hopk.  U.  S.)  Alabama:  Calhoun,  Montgomery. 
Arkansas:  Hampton.  Georgia:  Clyo,  Thomasville,  Demorest.  Louisi- 
ana: Singer,  Wilson.  Maryland:  Near  Cumberland.  North  Carolina:  \ 
Tryon,  Pisgah  Ridge,  Fletchers,  Boardman,  Pink  Beds,  Biltmore. 
South  Carolina:  Chicora  (Pregnalls).  Tennessee:  Ducktown.  Texas: 
Call,  Deweyville,  Kirbyville,  Beaumont.  Virginia:  Green  Bay,  Glen 
Allen,  Auburn  Mills,  Virginia  Beach.  District  of  Columbia :  Washington. 
Additional  localities  represented  in  other  collections:  (Le  Conte)  Lake 
Superior,  Michigan.  (There  may  have  been  some  mistake  in  regard  to 
the  labeling  of  this  specimen,  since  it  is  not  likely  the  species  will  ever 
be  found  that  far  north.)  (H.  &  S.)  Haw  Creek,  Florida ;  Cobbs  Island, 
Virginia;  (A.  M.  N.  H.)  Black  Mountains  and  Mount  Graybeard, 
North  Carolina;  (Barber)  "  western  Indian  territory"  [Oklahoma]. 


THE   GENUS   DENDROCTONUS.  95 

Host  trees. — Pinus  strobus,  P.  t&da,  P.  rigida,  P.  virginiana,  P.  pun- 
,  P.  echinata,  P.  glabm,  P.  palustris,  Picea  rubens,  and  P.  excelsa. 

Identified  specimens. — Le  Conte  collection,  9;  Horn,  1;  U.S.N.M., 
II.  &S.,5;  D.A.,7;  Barber,  2;  Hopk.  W.  Va.,  68;  Hopk.  U.  S.,  more 
than  150,  including  all  stages  and  work. 

BIBLIOGRAPHY  AND  SYNONYMY. 

Dendroctonus  frontalis  Zimmerman,  1868,  p.  149,  original  description,  type/ locality , 
Carolina.  Le  Conte,  1868,  p.  173,  synopsis  and  reference  to  p.  149.  Xe  Conte, 
1876,  p.  386,  revision,  synopsis,  synonymy  excluded,  bibliography,  localities. 
Packard,  1887,  p.  177,  Le  Conte  quoted.  Packard,  1890,  p.  722,  Le  Conte  quoted. 
Dietz,  1890,  p.  32,  in  part,  fig.  6,  antennaand  epistoma.  Hopkins,  1892a,  pp.  64-65, 
depredations  in  W.  Va.  Hopkins,  1892b,  p.  353,  importation  of  enemy.  Schaufuss, 
1892,  p.  316,  introduction  of  enemy.  Hopkins,  1893a,  pp.  187-189,  habits,  etc. 
Hopkins,  1893b,  p.  143,  No.  77  and  index,  habits,  host,  distribution,  enemies. 
Hopkins,  1893c,  p.  213,  No.  301,  same  as  1893b.  Hopkins,  1893d,  pp.  123-129, 
habits  and  enemy.  Lintner,  1894,  p.  292,  reference  to  Hopkins.  Hopkins, 
1894a,  pp.  71-76,  same  as  Hopkins  1893d.  Hopkins,  1894c,  p.  348,  insects,  birds, 
and  forests.  Lintner,  1895,  same  as  1894.  Hopkins,  1896,  pp.  246-250,  disap- 
pearance in  W.  Va.,  occurrence  in  N.  C.  Hopkins,  1897a,  pp.  29-41,  importation 
and  distribution  of  enemy.  Hopkins,  1897b,  pp.  35-36,  enemy,  etc.  Hopkins, 
1897c,  pp.  79,  94,  95,  PL  I,  dead  trees,  fig.  IV,  Clerus formicarius  L.,  discussion  of 
habits,  etc.,  pp.  147,  151,  reprint  from  1896.  Chittenden,  1897,  pp.  67,  75,  fig. 
43,  adult,  destructive  habits.  Schwarz,  1898,  p.  81,  habits  and  disappearance. 
Hopkins,  1898b,  pp.  104-105,  habits,  etc.  Hopkins,  1899a,  pp.  394-414,  etc.  (see 
index),  full  account,  all  stages  and  work  illustrated  and  described,  natural  ene- 
mies, hosts,  distribution,  bibliography,  etc.  Hopkins,  1899b,  pp.  11,  13,  14, 
reference  to  habits.  Hopkins,  1899c,  p.  343,  disappearance  in  W.  Va.  due  to  freez- 
ing. Chittenden,  1899,  pp.  55,  56,  fig.  5,  habits,  etc.  Ulke,  1902,  pp.  36,  56,  host, 
habits,  etc.,  in  D.  C.  Hopkins,  1903a,  p.  59,  occurrence  and  habits  in  southern 
States.  Hopkins,  1903b,  pp.  270,  275,  figs.  26,  27,  28-32,  stages  and  work,  with 
account  of  habits,  life  history,  etc.  Hopkins,  1904,  pp.  41,  42,  44,  PL  I,  fig.  2, 
PI.  VII,  figs,  a,  b,  stages  and  work,  account  of  distribution,  habits,  etc.  Felt, 

1905,  p.  6,  reference.     Hopkins,  1906c,  p.  81,  mentioned  in  comparison.    Webb, 

1906,  pp.  20,  22,  mentioned.     Hopkins,  1908,  p.  163,  depredations. 
Bostrichus  frontalis  (not  of  Fab.)  Zimmerman,  1868,  p.  149,  synonymical  reference. 

Le  Conte,  1868,  p.  173. 

Dendroctonus  pinicida  Hopkins,  1902a,  p.  3,  manuscript  name  only. 
l)i  1 1  droctonus  frontalis  Zimm.  var.  destructor  Hopkins,  1902b,  p.  21,  note.     Hopkins, 

1902c,  p.  20,  habits,  etc. 
Dendroctonus  brevicornis  Dietz,  1890,  p.  32  (in  part). 

5.     Dendroctonus  arizonicus  n,  sp.  $ 

(PI.  Ill,  fig.  5.) 

Adult. — Type  of  species,  female:  Length,  3.7  mm.,  dark  brown. 
Elytra!  declivity  with  long  hairs  confined  to  declivity  and  posterior 
lateral  areas.  Head  with  front  convex,  shining,  and  with  distinct 
frontal  tubercle  each  side  of  a  broad  median  groove.  Elytral  striae 
distinctly  punctured;  the  interspaces  with  subacute,  moderately 
coarse  rugosities,  distinctly  coarser  toward  the  base  and  vertex. 
Pronoturn  with  long  erect  hairs  on  the  anterior  half  of  the  lateral 
area.  Secondary  sexual  characters  same  as  in  D.  frontalis. 


96 


THE   SCOLYTID   BEETLES. 


Type  labeled  "Type   No.  7446,  U.S.N.M.,"  name  label,  "Hopk. 
1/15/05,    9 ,  Barber    &    Schwarz    Collectors],  Williams,  Ar.,    7.6 
(-June  7). 

Male  type:  Length,  3.3  mm.  Front  with  prominent  tubercles  each 
side  of  a  deep  median  groove.  Pronotum  with  transverse  impression 
and  faint  transverse  elevation  across  anterior  area.  Elytral  declivity 
less  shining;  striae  more  distinctly  impressed  and  punctured  and  the 
interspaces  more  convex  and  distinctly  rugose  than  in  the  female. 

Male  type  labeled,  name  label,  "Hopk.  Jan.  l5/Q8,Pinusponderosa, 
Webb,  Collr.,  8-22-04,  Flagstaff,  Ariz.,  $  ,  Hopk.U.  S.  No.  5118." 

Variations. — Length  3.5  to  3.9  mm.,  average  about  3.6  mm.;  color 
from  light  brown  to  black.  The  short  hairs  of  the  lateral  area 
of  the  elytra  range  from  obscure  to  distinct,  and  the  long  hairs  of 
the  elytral  declivity  range  from  short  and  sparse  to  very  long  and 
numerous.  The  variation  in  the  size  of  the  punctures  of  the  pronotum 
is  less  marked  than  in  other  species. 

Distinctive  characters. — The  coarse  punctures  of  the  pronotum,  and 
especially  the  very  coarse  shallow  rugose  ones,  together  with  the 
coarser  rugosities  of  the  elytra,  serve  to  distinguish  specimens  of 
this  species  from  D.  barberi,  and  the  absence  of  short  reclining  hairs 
on  the  pronotum  with  the  more  distinctly  impressed  elytral  striae 
and  less  evident  short  and  long  hairs  on  the  elytra  serve  to  distinguish 
it  from  D.  mexicanus,  which  is  its  nearest  ally.  It  is  also  distinguished 
from  D.frontalis  by  its  larger  size,  coarser  punctures  of  the  pronotum, 
and  coarser  rugosities  of  the  elytra,  as  it  is  from  small  examples  of  D. 
convexifrons  by  the  grooved  front,  and  from  small  examples  of  D. 
approximatus  by  the  impressed  elytral  striae  and  the  shorter,  more 
yellow,  and  less  numerous  hairs  of  the  declivity. 

Revisional  notes. — This  species  is  not  represented  in  the  Le  Conte 
collection  and  not  in  the  Horn  collection  unless  it  is  one  specimen 
found  under  D.frontalis  labeled  "Williams,  Ariz.,  7.28,  152,"  which 
the  writer  has  not  seen  since  D.  arizonicus  has  been  recognized  as  a 
distinct  species.  If  this  specimen  is  D.  arizonicus,  it  was  evidently 
before  Doctor  Dietz  when  he  prepared  his  revised  description  of  D. 
frontalis. 

Pupa. — In  addition  to  the  generic  and  divisional  characters,  the 
apices  of  the  front  and  middle  femora  have  each  a  small  spine.  Ab- 
dominal tergites  2  to  6  with  small  pleural  spines  and  4  to  6  with  small 
dorsal,  lateral,  and  pleural  spines,  increasing  in  size  toward  6;  7  and 
8  with  a  pair  of  dorsal  granules,  coarser  on  7.  Pupal  type  labeled 
"Hopk.  U.S.  No.  3129." 

Larva. — In  addition  to  the  divisional  characters,  the  front  has  a 
median  transverse  and  rugose  convexity  produced  toward  apex;  cly- 
peus  with  apex  broadly  emarginate;  labrum  broad,  with  apex  broadly 
rounded.  Thoracic  segments  with  foot  calli  on  sternellar  lobes. 
Larval  type  labeled  "Hopk.  U.  S.  No.  5156." 


THE   GENUS   DENDROCTONUS. 


97 


Galleries. — While  the  galleries  of  this  species  have  not  been  defi- 
nitely recognized  from  those  of  D.  barberi,  with  which  they  are  nearly 
always  present,  it  is  evident  that  they  are  quite  similar  in  general 
character  to  those  of  D.  barberi,  especially  in  the  concealed  larval 
mines. 

Distribution  (fig.  58). — (Hopk.  U.  S.)  Arizona:  Williams,  Flag- 
staff, Santa  Catalina  Mountains  (rare). 

Host  tree. — Pinus  ponderosa  var.  scopulorum. 

Identified  specimens. — Horn  collection,  1  (?),  B.  &  S.,  2;  Hopk. 
U.  S.,  more  than  50  specimens,  including  adults,  larvae,  and  pupae. 

BIBLIOGRAPHY. 
Dendroctonus  arizonicus  Hopkins,  1902a,  p.  3  (in  part),  manuscript  name. 


FIG.  58. — Dendroctonus  arizonicus:  Distribution  map.    (Original.) 
6.     Dendroctonus  mexicanus  Hopkins. 

(PL  III,  fig.  6.) 

Adult. — Type  of  species,  female:  Length,  4  mm.;  dark  brown. 
Slytra  with  long  hairs  on  posterior  half  and  declivity.  Head  with 
ront  convex,  shining,  with  small  frontal  tubercles  each  side  of  the 
hort,  shallow  groove;  elytral  striae  distinctly  impressed,  but  not  dis- 
inctly  punctured;  elytral  rugosities  distinctly  coarser  toward  the 
>ase  and  vertex,  and  with  an  evident  row  of  acute  rugosities  on  the 
irst  interspace.  Pronotum  clothed  with  short  reclining  hairs  on 
intire  lateral  area.  Secondary  sexual  characters:  Pronotum  with 
Tansverse  ridge  across  the  anterior  area;  elytral  declivity  shining, 
striae  distinct,  obscurely  punctured;  interspaces  roughened  with 
sparsely  exposed  granules,  becoming  coarser  toward  the  vertex  in 
ateral  area. 

79980—09 8 


98 


THE    SCOLYTID   BEETLES. 


Type  labeled  "Type  No.  7518,  U.S. N.M.,  individual  l/'name  label, 
un.  sp.,  Hopk.,  4/18/02,"  name  label,  "  1/15/08,  A.  L.  Herrera,  col- 
lector, 9  ,  Sacramento,  Amecameca,  Mexico." 

Male  type:  Length,  4  mm.;  front  with  moderately  prominent  fron- 
tal tubercles  each  side  of  the  distinct  groove.  Pronotum  with  rather 
distinct  transverse  elevation  across  the  entire  area  similar  to  that  of 
the  female;  elytral  declivity  more  uniformly  convex;  striae  more 
impressed  and  deeply  punctured  and  interspaces  more  convex  and 
distinctly  rugose. 

Male  type  labeled  "Type  No.  7518,  U.S.N.M.,  individual  5,"  remain- 
ing labels  same  as  on  female  except  sex  label. 

Variations. — Length  from  3  to  4.5  mm.;  aver^ 
age  about  3.8  mm.;  color  from  brown  to  black. 
The  prescutal  ridge  is  more  prominent  in  some 
females  than  in  others  and  is  present  in  some 
males  and  absent  in  others. 

Distinctive  characters. — This  species  is  more 
closely  allied  to  D.  arizonicus  than  to  any  of  the 
other  species  of  the  division  to  which  it  belongs 
and  is  distinguished  from  it  by  the  presence  of 
short,  recjining  hairs  on  the  pronotum,  less  dis- 
tinctly impressed  elytral  striae,  and  more  evident 
short  pubescence  of  the  elytra. 

Revisional  notes. — It  is  evident  that  this  spe- 
cies was  not  represented  in  the  material  studied 
by  Blandford.  The  size  comes  near  that  of  his 
D.  adjunctus,  but  the  characters  as  given  by 
him  to  distinguish  this  species  from  D.  parallel- 
ocollis  at  once  distinguish  it  from  D.  mexicanus. 
The  pupa  and  larva  have  not  been  seen. 
Gallery  (fig.  59). — A  small  section  of  the  gal- 
lery, evidently  of  this-  species,  was  received  with  the  specimens  of 
adult  from  Prof.  A.  L.  Herrera. .  This  indicates  a  winding  egg  gallery, 
with  the  eggs  isolated,  the  larval  mines  concealed  in  the  inner  bark, 
and  the  pupal  cells  in  the  outer  bark. 

Distribution  (fig.  60)  and  Jiost  trees. — The  specimens  received  at  dif- 
ferent times  from  Prof.  A.  L.  Herrera  and  Dr.  S.  J.  Bonansea  were 
evidently  from  Pinus  teocotl,  P.  lejopMlla,  and  P.  ayacahuite  in  Ame- 
cameca, Michoacan,  and  Tacubaya,  Mexico. 

Identified  specimens. — Thirty-six  specimens  of  adults  and  one  speci- 
men of  work  were  identified  for  Professor  Herrera  and  Doctor  Bonan- 
sea, a  set  of  which  were  returned  to  them  and  the  remainder  retained  ; 
for  the  forest  insect  collection  of  the  Bureau  of  Entomology. 


FIG.  59. — Dendroctonus  mex- 
icanus: Section  of  egg  gal- 
leries. (Original.) 


THE   GENUS   DENDROCTONUR. 
BIBLIOGRAPHY. 


99 


Jtcndroctonus   mexicanus    Hopkins,   1906c,   p.  80,   original    description,    both  sexes, 
host.  etc. 


FIG.  60. — Dendroctonus  mexicanus:  Distribution  map.    (Original.) 
7.     Dendroctonus  parallelocollis  Chapuis. 

(PI.  Ill,  fig.  7.) 

Adult. — Typical  female:  Length,  6.1  mm.,  deep  black;  elytral  decliv- 
ity with  long  hairs;  head  with  front  convex,  shining,  without  dis- 
tinct frontal  tubercles  each  side  of  the  shallow  median  groove ;  elytral 
striae  not  impressed  or  distinctly  punctured  except  at  vertex;  elytral 
rugosities  obtuse,  rather  densely  placed,  moderately  coarse  toward 
suture,  fine  and  less  evident  toward  and  on  the  lateral  area;  striae 
obscure,  especially  on  the  lateral  area.  Pronotum  with  numerous 
short,  reclining  hairs  and  with  very  long,  erect  hairs  on  the  entire 
lateral  area,  punctures  distinct.  Secondary  sexual  characters:  Pro- 
notum with  transverse  ridge  across  the  anterior  area;  elytral  declivity 
subconvex,  shining;  striae  distinct,  slightly  impressed,  punctures 
rather  distinct;  interspaces  with  a  few  granules  and  sparse  punctures, 
the  lateral  areas  more  rugose  and  coarsely  punctured. 

Typical  female  labeled,  name  label,  "Hopk.,  January  16/08, 
liichoacan,  Mexico,  A.  L.  Herrera,  collector,  9  ,  Hopk.  U.  S.  2896b." 

Typical  male:  Length,  6  mm.  Head  with  front  convex  and  with 
prominent  frontal  tubercles  each  side  of  a  deep  groove.  Pronotum 
with  transverse  impression  across  anterior  area;  elytral  declivity 


100 


THE   SCOLYTID   BEETLES. 


subconvex;  striae   distinct,   slightly  impressed,   and   the  interspaces 
more  distinctly  rugose  than  in  female. 

Typical  male  labeled,  name  label,  "Hopk.  1/16/08,  type  of  draw- 
ing, Pinus,  Michoacan,  Mexico,  A.  L.  Herrera,  collector,  $ ,  Hopk. 
U.  S.  2896a." 

Variations. — Length  from  5  to  6.1  mm.,  average  about  5.5  mm.; 
color,  dark  brown  to  black,  with  the  usual  variation  in  epistoma,  pro- 
notal  punctures,  pubescence,  and  median  line. 

Distinctive  characters. — This  species  is  distinguished  from  D. 
approximates  by  the  noticeably  less  shining  and  more  pubescent  pro- 

notum,  the  deeper  punctures,  the 
noticeably  and  constantly  less  im- 
pressed elytral  striae,  and  the  less 
distinct  punctures. 

Revisional    notes. — Agrees    with 
original    description,    except    that 
the  specimens  before  the  writer  are 
smaller,  the  type  being  given  as  6§ 
mm.     The  median  line  is  flat  in  all 
but  one  specimen,  in  which  it  is  im- 
pressed  toward  the   anterior  and 
posterior  margin.     In  Blandford's 
revision  the  length  of  the  type  is 
given  as  6.3  mm.    Blandford  states 
that  it  differs  from  D.  approxima- 
tus  Dietz  by  its  smaller  size,  more 
elongate  shape,  more  shining  and 
strongly  punctured  prothorax,  and 
indistinct  elytral  striae.  The  last  dif- 
ference holds,  but  the  others  do  not. 
In  the  writer's  reference  to  this 
species  (1905a,  p.  81)  it  was  con- 
sidered to  be  the  same  as  D.  approximatus  Dietz,  but  I  am  now  con- 
vinced that  the  two  are  specifically  distinct. 
The  pupae  and  larvae  have  not  been  observed. 
Galleries  (fig.  61). — A  short  section  of  the  egg  gallery,  from  which 
an  adult  was  taken,  indicates  that  it  is  quite  similar,  in  its  winding 
character  and  the  absence  of  exposed  larval  mines,  to  that  of  D. 
approximatus. 

Distribution  (fig.  62). — Recorded  from  Mexico  by  Chapuis  (1869) 
and  Blandford  (1897).  Specimens  were  received  with  D.  mexicanus 
from  Prof.  A.  L.  Herrera,  labeled  Mexico  and  Michoacan,  Mexico, 
with  his  statement  that  it  destroys  the  forests  of  lonacatapec,  Morelos, 
and  many  regions  of  Mexico. 


FIG.  61.— Dendroctonus  parallelocollis:  Section  of 
egg  gallery.    (Original.) 


THE   GENUS   DENDROCTONUS'. 


101 


Host  trees. — According  to  evidence  from'  corresponderlce  with 
Professor  Herrera,  it  would  appear  that  this  species,  like  D.  mexi- 
canus,  attacks  Pinus  teocotl  (?),  P.  lejophllla,  and  P.  ayacahuite, 
although  there  is  no  definite  statement  to  that  effect.  It  is  quite 
evident,  however,  that  this  species  is  associated  with  D.  mexicanus 
in  the  same  manner  as  D.  approximatus  in  its  association  with  D. 
arizonicus  and  D.  barberi. 

Identified  specimens. — Ten  specimens  of  adults  and  one  specimen  of 
work  identified  for  Prof.  A.  L.  Herrera. 


FIG.  62— Dendroctonus  parallelocollis:  Distribution  map.     (Original.) 

BIBLIOGRAPHY. 

Dendroctonus  parallelocollis  Chapuis,  1869,  p.  36,  original  description.  Chapuis, 
1873,  p.  244,  reprint.  Blandford,  1897,  p.  147,  synopsis,  revision,  distribution, 
bibliography.  Hopkins,  1906c,  p.  81,  systematic  notes. 

8.     Dendroctonus  approximatus  Dietz. 

(PI.  IV,  fig.  8.) 

Adult. — Typical  female:  Length,  6.5  mm.,  reddish  brown;  elytral 
declivity  with  long  hairs;  head  with  front  convex,  shining,  and  with 
obscure  frontal  tubercles  each  side  of  short,  median  groove;  elytral 
striae  not  impressed  or  distinctly  punctured;  elytral  rugosities  rather 
coarse,  sparse;  striae  on  lateral  area  rather  distinct;  pronotum  with 
long  hairs  on  anterior  two-thirds  of  lateral  area,  but  not  on  posterior 
section.  Secondary  sexual  characters:  Pronotum  with  transverse 
ridge  across  the  anterior  area;  elytral  declivity  subconvex,  shining; 


102 


THE    SCOLYTID   BEETLES. 


striae  very  distinct,  impressed,  and  distinctly  puncturedj  interspaces 
sparsely  tuberculate,  and  with  a  few  fine  punctures;  lateral  area 
shining,  with  a  few  subacute  tubercles,  and  rather  coarse,  distinct 
punctures. 

Typical  female  labeled,  name  label,  "Hopk.  1/16/08,  9  ,  individual 
c,  Barber  &  Schwarz,  Collectors],  Flagstaff,  Ar.  2.7"  (  =  July  2). 

Type  of  species,  9 ,  in  Horn  collection,  A.E.S.,  Philadelphia, 
labeled  "Type  D.  approximates  n.  sp.,  Colorado]." 

Male  type:  Length,  5.7  mm.  Head 
with  front  convex,  shining,  a  prominent 
frontal  tubercle  each  side  of  a  deep 
groove.  Pronotum  with  broad  impres- 
sion across  the  anterior  area;  elytral  de- 
clivity same  as  female,  except  that  the 
interspaces  are  more  densely  rugose. 

Male  type  labeled,  name  label,  "Hopk. 
1/16/08,  $  type  of  revision,  type  of 
drawing,  Williams,  Ar.,  7.6"  (  =  June  7) 
"  $  ,  Barber  &  Schwarz,  Coll [ec tors].'7 

Variations. — The  length  varies  from  4 
to  7.4  mm.,  the  average  about  6  mm. 
The  color  ranges  from  reddish-brown  to 
black.  The  epistomal,  frontal,  pronotal, 
and  elytral  sculpture  and  vestiture  vary 
as  usual.  The  greatest  variation  is  in 
the  s trial  and  interspacial  punctures  of 
the  declivity. 

Distinctive  characters. — The  characters 
which  distinguish  this  species  from  D. 
parallelocollis ,  its  nearest  ally,  are  the 
noticeably  more  shining  and  less  pubes- 
cent pronotum,  with  the  punctures  finer 
and  more  shallow,  the  elytral  striae  con- 
stantly more  impressed,  and  the  punc- 
tures distinct. 

Eevisional  notes. — The  original  description  (Dietz,  1890,  p.  31),  was 
based  on  "four  specimens,  two  males  and  two  females,  from  New 
Mexico  and  Colorado  in  Doctor  Horn's  collection."  The  specimen 
labeled  type  in  the  Horn  collection  is  a  female  from  Colorado,  and 
agrees  with  the  description,  but  one  specimen  labeled  "N.  M."  is  a 
female  of  D.  convexifrons  Hopk.,  and  one  other  specimen  with  the 
type,  but  without  locality  label,  is  quite  a  different  thing  from  either 
of  the  other  two.  The  specimen  has  not  been  examined  since  the 
more  distinctive  characters  of  D.  monticolse  Hopk.  and  D.  ponderosse 
Hopk.  have  been  recognized,  but  it  evidently  belongs  to  one  of  these 
species.  The  fourth  specimen  mentioned  by  Dietz  was  not  in  the 


FIG.  63.—Dendroctonus  approximates: 
Single  egg  gallery.    (Original.) 


THE   GENUS   DENDROCTONUS. 


103 


collection  when  examined  by  the  writer  on  January  12,  1900.  The 
reference  in  the  original  description  to  the  front  of  the  head  "  coarsely 
granulated,  channeled"  applies  to  the  type,  and  at  once  distinguishes 
it  from  the  other  two  specimens  which  are  without  a  median  frontal 
channel  or  groove.  The  "  strong  transverse  impression  about  one- 
fourth  from  the  an- 
terior margin"  of  \  l"sN^  I  )M  I  j  / 
the  prothorax  is  as-  r\V  //<  I  () 
sociated  with  the 
more  distinct  trans- 
verse  elevation 
which  the  author 
Failed  to  mention. 
In  the  writer's  re- 
marks (Hopkins, 
1905,  p.  81)  under 
D.  parallelocollis  it 
is  stated  that  D. 
parallelocollis  Chap . 
and  D.  approxima- 
tus  Dietz  are  evi- 
dently the  same, 
but  further  com- 
parative studies 
have  convinced 
him  that  they  are 
specifically  distinct. 

Pupa. — In  addi- 
tion to  the  generic, 
divisional,  and  sub- 
divisional  charac- 
ters, the  apex  of  the 
front  and  middle 
femora  have  each  a 
minute  subapical 
s  p  in  e  ;  abdominal 
tergites  1  to  6  with 
small  pleural  spines, 
1  without  distinct 
dorsal  and  lateral  spines;  2  to  6  with  distinct  dorsal  and  lateral 
spines,  increasing  in  length  and  prominence  to  and  including  tergite 
6;  7  and  8  smooth;  9  with  long  pleural  spine.  Pupal  type  labeled 
"Hopk.  U.  S.  No.  5777." 

Larva. — In  addition  to  generic  and  divisional  characters,  the  front 
has  a  broad,  but  not  prominent,  median  elevation;  clypeus  short, 
broad,  with  apex  truncate;  pro  thoracic  segments  with  prominent 


FIG.  64.— Dendroctonus  approximates:  Egg  galleries.    (Original.) 


104 


THE    SCOLYTID   BEETLES. 


sternellar  lobes,  each  with  a  distinct  foot  callus.  Larval  type  labeled 
"Hopk.  U.  S.  No.  5024." 

Galleries  (figs.  63,  64). — Egg  galleries  sublongitudinal,  branched, 
slightly  winding;  eggs  isolated;  larval  mines  concealed;  pupal  cells  in 
outer  bark. 

Distribution  (fig.  65).— (Hopk.  U.  S.)  Colorado:  Brookville,  Glen 
Haven,  Las  Animas  County,  La  Veta,  Monte  Vista,  and  Palmer  Lake. 
Utah:  Escalante,  Kamas,  Panguitch.  New  Mexico:  Capitan  Moun- 
tains, Cloudcroft,  Lincoln  National  Forest,  Santa  Fe.  Arizona: 
Black  Mesa  Forest  Reserve,  Chiricahua  Mountains,  Flagstaff,  Para- 
dise, Rincon  Mountains,  Santa  Catalina  Mountains,  Show  Low, 
Tucson.  Additional  locality  from  correspondence:  Glenhaven,  Colo. 


T 


\   La?fe*  r 

vw^sy — 

.,-^:»!?/-::;:-?t~] 


:-';:-«iv'->;..  i 


FIG.  65.— Dendroctonus  approximates:  Distribution  map.    (Original.) 

Host  trees. — Pinus  ponderosa  scopulorum  (common),  P.  arizonica 
(rare),  and  P.  chihuahuana  (rare). 

Identified  specimens. — Horn,  A.  E.  S.,  1  specimen,  the  type; 
U.S.N.M.,  31;  Hopk.  U.  S.,  more  than  200  specimens,  including  all 
stages  and  work. 

BIBLIOGRAPHY  AND  SYNONYMY. 

Dendroctonus  approximatus  Dietz,  1890,  p.  31,  fig.  5,  antenna  and  epistoma;  original 
description  (applies  to  type  only).  Blandford,  1897,  p.  147,  reference  to  charac- 
ters. Hopkins,  1899a,  p.  392,  fig.  LVIII,  reference.  Schwarz,  1902,  p.  32  (in 
part),  destructive  to  pine  at  Flagstaff,  Ariz,  (see  also  convexifrons) .  Wickham, 
1902,  p.  310  (in  part),  list,  Dietz  quoted.  Hopkins,  1903a,  p.  60,  reference  to 
habits,  etc.  Hopkins,  1903b,  p.  281,  mention.  Hopkins,  1904,  p.  44,  habits,  dis- 
tribution, hosts,  etc.  Hopkins,  1905,  p.  11,  some  distinctive  characters.  Hopkins, 
1906c,  p.  81,  referred  to  D.  parallelocollis. 

Dendroctonus  (parallelocollis)  var.  approximatus  (Dietz)  Fall,  1907,  p.  218,  list, 
localities. 


THE   GENUS   DENDROCTONUS.  105 

SUBDIVISION  B. 
(Species  numbered  9  to  11,  inclusive.) 

The  distinctive  characters  common  to  the  species  of  the  second  sub- 
division are  as  follows: 

Adult. — Body  somewhat  stout,  prothorax  with  sides  distinctly  nar- 
rowed and  constricted  toward  the  head;  elytral  declivity  with  second 
stria  distinctly  curved,  second  interspace  broader  toward  middle,  nar- 
rowed toward  apex. 

Sexes. — Female:  Elytral  declivity  with  interspaces  smoother  and 

>re  shining,  mandibles  less  stout.     Male:  The  reverse. 

Pupa. — Elytral  pads   roughened  with  granules,   vertex  of  head 

jply  grooved  and  with  two  prominent  forward  curved  frontal  spines 
>ward  the  vertex;  abdominal  tergites  2  to  6  with  long  and  prominent 

iural  spines. 

Larva. — Front  with  prominent  transverse  and  rugose  elevation, 

>re  prominent  toward  the  sutures. 

Galleries. — Pupal  cells  in  inner  bark,  eggs  in  approximate  groups, 
galleries  slightly  winding  to  straight,  larval  mines  always  exposed 
in  inner  bark. 

9.     Dendroctonus  monticolse  Hopkins. 

(PI.  IV,  fig.  9.) 

Adult. — Type  of  species,  female:  Length  5.6  mm.,  light  brown; 
elytral  declivity  with  a  few  long  hairs;  head  with  front  convex,  with- 
out median  elevation  or  groove,  but  with  faint  posterior  impression; 
elytral  rugosities  coarse,  rather  dense,  coarser  on  dorsal  area;  striae 
not  distinctly  impressed,  except  toward  suture,  punctures  small. 
Pronotum  with  the  anterior  area  transversely  impressed,  but  with 
moderately  long  hairs  on  the  lateral  area,  slightly  longer  on  the  ante- 
rior section.  Secondary  sexual  characters :  Elytral  declivity  convex, 
subopaque;  striae  distinct,  and  impressed,  with  fine  obscure  punc- 
tures; interspaces  with  rather  coarse  granules,  in  approximate  rows; 
lateral  area  with  obscure  punctures  and  subacute  rugosities. 

Type  labeled  "No  7447  U.S.N.M.,"  name  label,  "Hopk.  1/16/08, 
Pinus  monticola,  Hopkins,  collector,  5/27/99,  Kootenai,  Idaho,  9 , 
Hopk.  U.  S.  205." 

Male  type:  Length  4.9  mm.  Head  with  front  less  distinctly  punc- 
tured and  more  rugose  than  female:  elytral  declivity  with  striae  more 
distinctly  punctured,  interspaces  more  opaque,  and  rugosities  slightly 
coarser,  the  mandibles  stouter  than  in  female. 

Male  type  labeled  same  as  female  except  sex  label. 

Variations. — The  length  varies  from  3.7  to  6.4  mm.,  averaging  about 
5.5  mm.  The  color  ranges  from  light  brown  to  black;  the  sculpture 
and  vestiture  of  the  epistoma,  front,  pronotum,  and  elytra  vary  as 
usual,  but  the  character  of  the  strial  punctures  is  fairly  constant. 


106  THE  SCOLYTID  BEETLES. 

The  greatest  variation  is  in  size  and  in  the  presence  or  absence  of 
dorsal  line  of  the  pronotum. 

Distinctive  characters. — The  characters  which  distinguish  this  spe- 
cies  from  the  next  following,  to  which  it  is  more  closely  allied,  are 
the  average  smaller  size  and  prevailing  moderately  impressed  elytral 
striae  with  distinct  but  moderately  coarse  punctures.  While  the  strial 
punctures  vary  in  size  in  different  individuals,  they  are  never  so  coarse 
as  in  the  average  D.  ponderosse.  It  is  also  distinguished  from 
D.  jeffreyl  by  the  much  smaller  average  length  of  body  and  the  pre- 
vailingly  coarser  punctures  of  the  pronotum. 

Revisional  notes.— A  brief  description  (Hopkins,  1905,  p.  11)  was 
published  under  the  name  D.  monticola,  but  the  name  should  read 
D.  monticolse,  which,  as  the  manuscript  name  indicates,  was  origi- 
nally intended.  The  species  is  represented  by  three  specimens  from 
California  in  the  Le  Conte  collection,  with  the  type  series,  under 
D.  similis,  bearing  specimen  numbers  4,  12,  and  13,  and  therefore 
may  have  been  included  in  the  revision  by  Le  Conte  (1876,  p.  385), 
although  the  locality  (California)  is  not  given  in  that  correction. 
There  is  also  one  specimen  in  the  Horn  collection,  labeled  "Cal.," 
under  D.  similis.  It  is  probable  that  the  one  under  similis  was  before 
Dietz  when  he  prepared  his  revision  (1890,  pp.  30-31)  under  the  name 
similis.  These  specimens  are  evidently  the  only  ones  which  may  have 
been  involved  in  Le  Conte's  or  Dietz's  revisions  on  the  literature  pre- 
vious to  Hopkins,  1899b,  pp.  14  and  26. 

Pupa. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  apex  of  the  front  and  middle  femora  is  armed  with 
two  small  apical  spines ;  abdominal  tergites  2  to  6  with  long  and  prom- 
inent pleural  spines,  1  is  without  distinct  dorsal  and  lateral  spines,  but 
2  to  6  have  distinct  dorsal  and  lateral  ones,  2,  3,  and  6  with  a  pair, 
and  4  and  5  with  three  lateral  spines  each  side  of  the  dorsal  ones; 
7  has  two  dorsal  spines,  while  8  is  smooth  and  the  pleural  spines  of  9 
are  long  and  prominent.  Pupal  type  labeled  "Hopk.  U.  S.  No.  196."? 

There  is  the  usual  variation  in  the  arrangement  and  number  of 
minor  spines,  and  one  specimen  from  Yosemite  National  Park  is  quite 
different  in  the  widely  separated  frontal  spines,  with  the  dorsal  ones 
of  the  abdominal  tergites  coarser  and  tergite  7  with  a  pleural  spine. 
It  is  possible  that  this  may  be  a  pupa  of  an  unrecognized  species. 
The  characters  of  the  pupa  of  D.  monticolse,  which  serve  to  distinguish 
it  from  that  of  D.  ponderosse,  are  the  less  coarse  spines  of  the  abdom- 
inal  segments,  the  less  densely  granulated  elytral  pads,  and  the  pres- 
ence of  two  apical  spines  on  the  front  and  middle  femora. 

Larva. — In  addition  to  the  generic  and  divisional  characters,  the 
front  has  the  posterior  angle  su'bacute  and  a  moderately  stout,  rugose 
elevation  situated  in  the  middle,  becoming  slightly  thickened  and 
elevated  toward  the  suture.  Clypeus  shining,  with  faint  median 


THE   GENUS   DENDROCTONUS. 


107 


groove  and  usual  elevation;  apex  broadly  emarginate,  labrum  with 
apex  broadly  rounded,  and  the  sternellar  lobes  of  the  thoracic  seg- 
ments with  distinct  foot  calli.  Larval  type  labeled  "Hopk.  U.  S. 
No.  196." 

There  is  some  variation  in  the  frontal  elevation,  but  generally  it  is 
situated  slightly  anterior  to  the  middle  or  in  the  middle,  while  the 
posterior  angle  of  the  front  is  distinctly  subacute.  These  serve  as 


FIG.  66. — Dendroctonus  monticolse:  Egg  galleries  and  larval  mines  in  bark.    (Original.) 

the  most  distinctive  characters  to  separate  the  larva  of  this  species 
from  that  of  D.  ponder  osse. 

Galleries  (figs.  66,  67). — The  egg  galleries  are  longitudinal,  distinctly 
to  slightly  winding  or  straight,  usually  grooved  on  the  surface  of 
the  wood  and  deeply  grooved  in  the  bark,  the  larval  mines  and  pupal 
cells  exposed  in  the  inner  bark;  the  eggs  are  placed  in  approximate 
groups,  and  the  larval  mines  are  short  and  broad.  The  egg  galleries 
differ  from  those  of  D.  ponderosse  in  smaller  size,  more  winding  form, 
and  are  often  of  a  much  greater  length. 


108  THE  SCOLYTID  BEETLES. 

Distribution  (fig.  68). — (Hopk.  U.  S.)  California:  Alder  Creek 
Chester,  Fulda,  Lake  Tenaya,  Mariposa  Grove,  Millwood,  Siskiyou 
County,  Soda  Springs,  Summerdale,  Tioga  Road,  Wawona.  Idaho 
Boise  County,  Cedar  Mountain,  Centerville,  Coeur  d'Alene  Nationa 


FIG.  67.— Dendroctonus  monticolse:  Egg  galleries  and  larval  mines  grooved  In  surface  of  wood.   (Original.) 

Forest,  Collins,  Helena,  Kootenai,  Moscow  Mountains,  Sand  Point, 
Smith's  Ferry,  Weiser.  Montana:  Big  Fork,  Columbia  Falls,  Iron 
Mountain,  Lolo,  Lewis  and  Clark  National  Forest,  Missoula,  Saltese. 
Oregon:  Ashland,  Grants  Pass,  Joseph,  Pokegama,  Wallowa.  Wash- 
ington: Longmires  Springs,  Mount  Rainier  National  Forest,  Pialschie, 


THE   GENUS   DENDROCTONUS. 


109 


(Washington  National  Forest.  Doming:  North  Fork  Shoshone 
i River,  Wapiti.  Additional  localities  from  other  collections:  (A.  M. 
ft  H.)  Millwood,  CaL;  (U.S.N.M.)  Columbia  Falls,  Mont. 

Host  trees. — Pinus  lambertiana,  P.  monticola,  P.  murrayana  and  P. 
oonderosa  (common);  Picea  engelmanni  (rare). 

Identified  specimens. — Le  Conte,  M.  C.  Z.,  3;  Horn,  A.  E.  S.,  1; 
k.  M.  N.  H.,  Webb  collection,  1;  Henry  Edwards  collection,  1; 
[J.S.N.M.,  2;  D.  A.,  11;  Webb  collection,  14;  Hopk.  U.  S.,  over  500, 
ncluding  different  stages  and  work. 


*V     •   •   '-V  .> 


FIG.  68.— Dendroctonus  monticolse:  Distribution  map.    (Original.) 
BIBLIOGRAPHY  AND  SYNONYMY. 

Dendroctonus  similis  (not  of  Le  Conte,  1860)  Le  Conte,  1876,  p.  385  (in  part),  locality. 
Dendroctonus  n.  sp.  Hopkins,  1899b,  pp.  14,  26,  first  record  of  habits  and  hosts. 
Dendroctonus  monticola  Hopkins,  1901b,  p.  67,  referred  to  as  new  species  but  not 

described,    habits,    galleries.     Hopkins,    1902c,   p.    21,   notes.     Hopkins,  1905, 

p.  11,  first  description,  distribution,  characters,  very  brief.     Webb,  1906,  p.  22, 

mentioned. 

Dendroctonus  monticolse,  Hopkins,  1902a,  p.  3,  manuscript  name. 
De/idroctonus  n.  sp.  (mountain  pine  Dendroctonus).     Hopkins,  1904,  pp.  19,  42,  45, 

habits,  hosts,  distribution,  etc. 
'.Mountain  pine  beetle.     Hopkins,  1908,  p.  162. 

10.     Dendroctonus  ponderosse  Hopkins. 
(PI.  IV,  fig.  10.) 

Adult. — Type  of  species,  female:  Length,  6  mm.,  black;  erytral 
declivity  with  a  few  long  hairs.  Head  with  front  convex,  without 
median  elevation  or  groove,  but  with  faint  posterior  impression; 
'lytral  rugosities  moderately  coarse  and  moderately  dense,  becoming 


110  THE  SCOLYTID  BEETLES. 

much  finer  on  the  lateral  area  and  coarser  toward  and  on  the  -vertex. 
Pronotum  with  moderately  long,  erect  hairs  on  the  lateral  area,  con- 
siderably longer  toward  the  anterior  section;  punctures  of  elytral 
striae  distinct  and  coarse.  Secondary  sexual  characters  same  as  in 
preceding  species. 

Type  labeled  "Type  No.  7448  U.S.N.M.,"  name  label,  "Hopk. 
1/16/08,  Pinus  ponderosa,  Spearfish,  S.  D.,  7/1/00,  A.  D.  Hopkins, 
collector,  9  ,  Hopk.  U.  S.  434." 

Male  type:  Length  5.5  mm.     Characters  same  as  in  female,  except 
pronotum  with  very  dense,  subrugose  punctures  toward  the  anterior; 
margin,  the  elytral  rugosities  finer  and  less  dense;  elytral  declivity | 
with  coarser  interspacial  granules,  and  the  strial  punctures  slightly  | 
more  distinct. 

Male  type  labeled  same  as  female,  except  sex  label. 

Variations. — The  length  varies  from  4.5  to  7  mm.,  with  the  average 
about  6  mm.  The  color  ranges  from  brown  (in  young  specimens)  to 
black  in  matured.  The  sculpture  and  vestiture  of  the  epistoma,  front, 
pronotum,  and  elytra  vary  as  usual,  and  there  is  a  quite  noticeable 
variation  from  a  somewhat  slender  form  to  a  shorter  and  stouter  one. 
The  greatest  variation  is  in  length  and  in  the  size  and  density  of  the 
punctures  of  the  pronotum  and  of  the  striae  of  the  elytra. 

Distinctive  characters. — The  characters  which  distinguish  this  species 
from  the  one  following  are  its  average  smaller  size,  less  shining  pro- 
notum, with  coarser  and  deeper  punctures,  and  from  the  preceding 
by  its  average  larger  size  and  somewhat  stouter  form,  with  the  elytral 
striae  more  distinctly  impressed  and  the  punctures  distinctly  coarser. 
There  is  a  considerable  range  of  variation  in  these  characters,  but  the 
specimens  with  less  distinctly  impressed  striae  and  finer  punctures 
which  might  be  mistaken  for  D.  monticola  are  exceptional,  and  should 
cause  no  confusion  as  long  as  the  range  of  distribution  of  the  two 
species  is  so  distinct. 

Revisional  notes. — In  March,  1902,  the  writer  (Hopkins,  1902a, 
p.  3)  published  the  manuscript  name,  D.  ponder  osse,  without  descrip- 
tion of  any  kind,  and  in  April  of  the  same  year  (Hopkins,  1902b,  p.  10) 
he  gave  a  brief  description  under  D.  ponderosa,  but,  as  indicated  by 
the  manuscript  name,  it  was  intended  that  the  name  should  relate  to 
the  host  tree,  Pinus  ponderosa,  therefore  the  name  D.  ponderosse,  under 
which  it  is  here  fully  described,  should  stand.  The  species  is  repre- 
sented in  the  Le  Conte  collection  by  one  immature  example,  which, 
in  1900,  was  in  the  D.  rufipennis  series,  labeled  "Specimen  8,  Col." 
In  March,  1907,  this  specimen  was  again  examined  by  the  writer,  and 
identified  as  D.  ponderosse.  It  is  evident  that  it  was  in  Le  Conte's 
collection  when  he  prepared  his  latest  revision  (1876),  but  there  is 


THE   GENUS   DENDROCTONUS.  Ill 

evidence  that  the  characters  and  locality  were  not  involved  in  the 
revised  description  under  D.  rufipennis.  It  is  probably  represented 
in  the  Horn  collection  (A.  E.  S.)  by  one  specimen,  without  locality 
label,  found  by  the  writer  in  1900  as  the  third  specimen  in  the  type 
series,  under  D.  approximatus.  Two  other  specimens,  labeled  "Colo.," 
were  found  in  the*  Horn  collection  and  one  specimen  in  the  general 
Aejulemy  of  Natural  Sciences  collection  under  D.  rufipennis.  The 
two  in  the  Horn  collection  were  evidently  before  Dietz  when  he  pre- 
pared his  revision  under  D.  rufipennis  and  included  in  the  Colorado 
locality  if  not  in  the  revised  description.  The  writer  (1902,  p.  10) 
refers  in  a  footnote  to  wrong  identifications  under  D.  rufipennis  and 
D.  terebrans.  This  probably  includes  all  of  the  published  references 
in  which  this  species  has  been  in  any  manner  involved  in  revisions 
or  systematic  notes. 

Pupa. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  front  and  middle  femora  are  armed  each  with  one  small 
apical  spine.  Abdominal  tergites  2  to  6,  with  long  and  prominent 
pleural  spines ;  1  is  without  distinct  dorsal  and  lateral  spines,  but  2  to 
6  have  distinct  dorsal  and  lateral  ones,  and  all  of  them  have  a  pair  of 
dorsal,  and  2,  3,  and  6  have  a  pair,  and  4  and  5  have  three  lateral 
spines  each  side  of  the  dorsal  ones;  7  has  two  dorsal  spines,  while  8 
is  smooth,  and  the  pleural  spines  of  9  are  long  and  prominent.  Pupal 
type  labeled  "Hopk.  U.  S.  No.  623." 

In  a  number  of  individuals,  the  usual  variation  in  the  arrangement 
and  number  of  minor  spines  is  found,  and  between  the  younger  and 
older  examples  there  is  a  wide  range  of  variation. 

The  characters  which  seem  to  distinguish  the  pupa  of  this  species 
from  that  of  D.  monticolse  are  the  coarser  spines  of  the  abdominal  ter- 
gites, the  more  densely  granulate  elytral  pads,  and  the  presence  of  but 
one  apical  spine  on  the  front  and  middle  femora. 

Larva. — In  addition  to  the  generic  and  divisional  characters,  the 
front  has  the  posterior  angle  subobtuse,  and  a  stout  prominent 
rugose  transverse  elevation  situated  slightly  behind  the  middle  and 
elevated  and  broad  toward  the  sutures;  clypeus  with  the  base  shining 
and  bearing  a  faint  median  elevation,  and  the  apex  broadly  emargi- 
nate;  labrum  less  than  half  as  long  as  broad,  with  the  apex  truncate; 
sternellar  lobes  of  the  thoracic  segments  with  indistinct  foot  calli. 
Larval  type  labeled  "Hopk.  U.  S.  No.  755." 

There  is  some  variation  in  the  frontal  elevation,  but  generally  it 
is  situated  behind  the  middle,  and  the  posterior  angle  of  the  front  is 
more  obtuse  than  in  the  preceding,  which  latter  serves  as  the  most 
distinctive  character  separating  the  larva  of  this  species  from  that  of 
D.  monticolx. 


112 


THE   SCOLYTID   BEETLES. 


Galleries  (figs.  69,  70). — The  egg  galleries  are  longitudinal,  and 
usually  nearly  straight.  They  are  usually  grooved  on  the  surface  of 
the  wood  and  deeply  grooved  in  the  inner  bark,  with  the  larval  mines 
and  pupal  cells  exposed.  The  eggs  are  placed  in  approximate  groups, 


FIG.  69.— Dendroctonus  ponderosx:  Egg  galleries  and  larval  mines.    ( Original.) 

and  the  larval  mines  are  short.     The  egg  galleries  differ  from  those 
of  D.  monticolx  in  the  larger  diameter  and  straighter,  shorter  form. 
^  Distribution   (fig.   71).— (Hopk.   U.   S.)   Arizona:  Chiricahua  Na- 
tional Forest,  Flagstaff,  Fredonia,  San  Francisco  Mountains.     Colo- 
rado: Bailey,  Brookvale,  Cascade,  Cat  Mountain,  Cochetopa,  Colo- 


THE   GENUS   DENDROCTONUS. 


113 


rado  Springs,  Fort  Garland,  Glenwood  Springs,  Gunnison  National 
Forest,  Green  Mountain  Falls,  Hahns  Peak,  Husted,  Indian  Creek, 
Larkspur,  La  Vet  a,  Manitou,  Medicine  Bow  National  Forest,  Meeker, 
Monte  Vista,  Ouray  National  Forest,  Palmer  Lake,  Pikes  Peak,  Pine, 
Poncha  Springs,  San  Isabel  National  Forest,  San  Juan  National  For- 
est,  Sequache,  IJncompahgre  National  Forest,  White  River  National 
Forest.  New  Mexico: 
Gil  a  National  Forest, 
Yermejo.  South  Da- 
kota: Ouster,  Elmore, 
Hill  City,  Lead,  Nemo, 
Piedmont,  Sylvan  Lake. 
Utnli:  Escalante,  Ka- 
inas,  Kanab,  La  Salle 
National  Forest,  Pan- 
guitch,  Provo.  Wyo- 
ming: Downington,  En- 
campment, Keystone. 
Additional  locality  from 
oilier  collectors:  (Brown) 
Las  Animas  County, 
Colo.  Localities  report- 
ed by  correspondents: 
Eagle,  Florissant,  Idaho 
Springs,  Kennedy  Sta- 
tion, La  Vet  a,  Montrose, 
Pagosa  Springs,  Porter, 
San  Juan,Ute  Pass,  and 
West  Cliff,  Colo. 

Host  trees .  —  Pinus 
ponder  osa  scopulorum, 
P.  flexilis,  P.  murray- 
ana,  P.  strobiformis,  and 
Picea  engelmanni. 

Economic  relation  to 
forests. — This  species  is 
exceedingly  destructive 
to  the  pine  forests  of 
the  central  and  southern  Rocky  Mountain  region,  having  caused  a 
loss  of  forest  resources  worth  many  millions  of  dollars.  The  rock 
pine,  or  bull  pine  (Pinus  ponderosa  var.  scopulorum},  is  its  favorite 
host  tree,  but  it  attacks  and  kills  the  other  pines  and  infests  the 
spruce,  though  apparently  not  destructive  to  the  latter. 

Identified  specimens. — Le  Conte  (M.  C.  Z.),  1  specimen;  Horn  (A.  E. 
S.),  2  specimens;   A.   N.    S.,  2    specimens;   U.S.N.M.,  1  specimen; 
79980—09 9 


FIG.  70.—Dendroctonus  ponder  osse:  Tree  with  bark  removed,  show- 
ing egg  galleries  grooved  and  marked  on  surface  of  wood.  ( Orig- 
inal.) 


114 


THE   SCOLYTID   BEETLES. 


D.  A.,    14    specimens;    Gillette,    2    specimens  ;•  Hopk.  U.  S.,  more 
than  10,000  specimens,  including  all  stages  and  work. 

BIBLIOGRAPHY  AND  SYNONYMY. 

Dendroctonus  similis(not  of  Le  Conte,  1860)  Le  Conte,  1876,  p.  385  (in  part)  (in  col- 
lection 1890). 

Dendroctonus    approximates     Dietz,    1890,   p.   31   (in    part?)   (specimen   with  type 
series). 

Dendroctonus  ponderosse  Hopkins,  1902a,  p.  3,  manuscript  name  only.  Hopkins 
1903b,  pp.  275,  282,  p.  xxix,  figs.  28,  32,  stages  and  work  figured,  and  full  accoun 
of  habits,  life  history,  methods  of  control,  etc.  Hopkins,  1904,  pp.  41,  43,  44 
PL  I,  fig.  1,  Pis.  Ill,  VIII,  IX,  XII,  fig.  2,  stages  and  work  illustrated,  habits 
host,  distribution,  etc.  Hopkins,  1905,  pp.  1-24,  full  account  of  history,  hab 
its,  life  history,  work,  methods  of  control,  etc.,  Pis.  I,  II,  figs.  1-6,  stages  am 
work.  Hopkins,  1906a,  p.  4,  old  work.  Hopkins,  1906b,  p.  147,  Pis.  IV,  V 
figs.  1-5,  anatomy  of  larval  head.  Fall,  1907,  p.  218,  list,  locality.  Hopkins 
1908,  p.  162,  depredations. 

Dendroctonus  ponderosa  Hopkins,  1902b,  p.  10,  brief  original  description,  adult,  etc. 
galleries  and  work  illustrated,  fig.  1,  Pis.  I,  III,  IV,  VII,  full  account  of  habits 
methods  of  control,  etc.  Hopkins,  1902c,  p.  21,  habits.  Hopkins,  1903a,  p.  59 
habits,  etc. 


WA 


yitlljlll\i^l 


X— r— r^ 


FIG.  71.— Dendroctonus  ponderosx:  Distribution  map.    (Original.) 

11.     Dendroctonus  Jeffrey!  n.  sp. 

(PI.  IV,  fig.  11.) 

Adult. — Type  of  species,  female:  Length  7.5  mm.,  black;  elytra 
declivity  with  a  few  long  hairs.  Head  with  front  convex,  with  slight 
anterior  and  posterior  impressions,  without  frontal  elevations;  elytra 
rugosities  moderately  coarse  and  dense,  becoming  much  finer  on  lat- 
eral area  and  coarser  toward  the  vertex.  Pronotum  shining,  sides 


THE   GENUS   DENDROCTONUS.  115 

distinctly  constricted  toward  the  head,  with  moderately  long,  erect 
liairs  on  the  lateral  area,  longer  and  denser  on  the  anterior  surface; 
punctures  of  elytral  striae  distinct  and  coarse,  the  striae  more  dis- 
tinctly impressed  on  the  dorsal  area.  Secondary  sexual  characters 
same  as  in  preceding  species. 

Type  labeled  ''  Type  No.  7440  U.S.N.M.,"  name  label,  "Hopk. 
1  22/08,  Pinus  jeffreyi,  Little  Yosemite,  Cal.,  H.  E.  Burke,  col- 
lector, ?,  Hopk.  U.  S.  4394a." 

Male  type:  Length  7  mm.,  same  characters  as  female,  except  ely- 
tral declivity  is  more  opaque  and  with  distinctly  coarser  interspacial 
rugosities. 

Male  type  labeled  same  as  female,  except  sex  label. 

]'(t rial-ions. — The  length  varies  from  6  to  8  mm.,  with  the  average 
about  7  nun.,  and  the  color  from  brown  in  young  specimens  to  deep 
black  when  matured.  The  sculpture  and  vestiture  of  the  epistoma, 
front,  pronotum,  and  elytra  vary  as  usual.  There  is  apparently  less 
variation  in  size  and  in  other  characters  than  is  found  among  the 
individuals  of  the  other  species. 

Distinctive  characters. — This  species  is  at  once  distinguished  from 
either  of  the  two  preceding  by  its  average  larger  size  and  shining  pro- 
notum, with  its  fine  and  shallow  punctures. 

Note. — This  species  is  not  represented  in  any  of  the  collections 
examined  by  the  writer,  and  nothing  has  heretofore  been  published 
about  it. 

Pupa. — In  addition  to  the  generic  and  divisional  characters,  the 
apices  of  the  front  and  middle  femora  are  armed  with  two  distinct 
spines;  abdominal  tergites  2  to  6  with  long  and  prominent  pleural 
spines;  1  is  apparently  without  dorsal  spines,  2  and  6  are  evidently 
with  dorsal  and  lateral  spines,  but  in  the  single  poor  specimen  the 
relative  size  and  number  can  not  be  made  out;  they  appear,  how- 
ever, to  be  less  prominent  than  in  either  of  the  preceding  species;  7 
has  two  small  dorsal,  three  distinct  lateral  spines,  and  a  small  pleural 
one;  8  is  smooth,  and  9  is  with  prominent  pleural  spines,  as  usual. 
Pupal  type  labeled  "Hopk.  U.  S.  No.  4412a." 

The  above  description  is  based  on  a  single  specimen,  which  is  dam- 
aged, therefore  is  subject  to  revision  when  more  specimens  are  exam- 
ined. It  seems  to  be  quite  different  from  the  unique  pupa  mentioned 
under  D.  monticola. 

Larva. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  front  has  the  posterior  angle  subacute,  and  a  narrow 
transverse  elevation  situated  in  the  middle  and  not  broadened  or 
more  elevated  toward  the  sutures;  clypeus  shining,  with  median 
groove  toward  the  base  and  with  the  apex  broadly  emarginate ;  labrum 
with  apex  broadly  truncate;  sternellar  lobes  of  the  thoracic  segments 


116 


THE   SCOLYTID   BEETLES. 


with  obscure  foot   scars.     Larval   type   labeled   "Hopk.  U.  S.  No. 
6204b." 

There  is  very  little  variation  in  the  four  specimens  before  the ' 
writer,  and  the  narrow  smoother  frontal  elevation,  not  elevated  and 
broadened  toward  the  suture,  is  the  most  distinctive  character  sepa- 
rating the  larva  of  this  species  from  those  of  the  two   preceding 
species. 

Galleries. — The    egg    galleries    are    longitudinal,    nearly    straight,  I 
grooved  on  surface  of  the  wood,  and  deeply  grooved  in  the  inner j 
bark,  with  the  larval  mines  and  pupal  cells  exposed.     The  eggs  are; 
placed  singly  and  in  approximate  groups.     The  egg  galleries  and  lar- 
val mines  of  this  species  differ  from  those  of  the  two  preceding  in 


FIG.  72.—Dendroctonusjeffrcyi:  Distribution  map.    (Original.) 

being  much  coarser;  otherwise  they  appear  to  be  more  like  those  oi 
monticolse. 

Distribution   (fig.   72).— (Hopk.  U.  S.)   California:  Chester,  Little*] 
Yosemite,    Nevada    City,    Pinogrande,    Sterling,    Tallac,  Yosemite 
(Yosemite  National  Park),  and  Seven  Oaks  (San  Bernardino  National] 
Forest). 

Host  trees. — Pinus  jeffreyi.  P.  ponderosa,  and  P.  lambertiana. 

Identified  specimens. — Hopk.  U.  S.,  over  160  specimens,  including! 
adults,  pupae,  and  larvae. 

DIVISION  II. 

The  distinctive  characters  common  to  the  species  of  the  second^ 
division  are: 

Adults. — Pro  thorax  stout,  usually  narrower  than  elytra,  distinctly 
narrowed  or  constricted  toward  head;  elytra  with  anterior  dorsal] 


THE   GENUS   DENDH<)(T<>NUS.  117 

half  bearing  long  hairs,  except  in  D.  terebrans  and  badly  nibbed  speci- 
mens. 

Pupa. — Vertex  of  head  faintly  impressed,  flat  or  convex,  and  with 
two  small  widely  separated  frontal  granules  toward  vertex. 

Larva. — Abdominal  tergites  8  and  9  with  dorsal  plates  except  in 
simplex  and  pseuUoisugx,  and  8  without  plate  in  micans. 

(rdlleries. — Egg  galleries  longitudinal,  straight  to  slightly  winding: 
eggs  in  groups  or  masses;  larval  mines  and  pupal  cells  exposed  in 
inner  bark. 

SUBDIVISION  (1. 
(Species  Nos.  12  to  21,  inclusive.) 

The  distinctive  characters  common  to  the  species  of  this  third  sub- 
division are: 

Adults. — Front  usually  with  posterior  impression,  pronotum  with 
large  and  small  punctures  intermixed.  Pronotum  with  long  hairs  on 
dorsal  and  lateral  areas. 

Sexes. — Female:  Interspaces  of  elytral  declivity  more  roughened 
and  the  striae  more  distinctly  impressed.  Male:  The  reverse. 

Pupa. — Vertex  of  head  flattened  or  faintly  impressed:  apices  of 
front  and  middle  femora  smooth;  abdominal  tergites  with  moderately 
prominent  pleural  and  dorsal  spines. 

Larva. — Abdominal  tergites  8  and  9  without  dorsal  plato  in  simplex 
and  pseudotsugoR  and  with  unarmed  dorsal  plate  in  the  remaining 
species. 

Galleries. — Egg  galleries  slightly  winding  to  straight;  eggs  in 
groups,  but  larval  mines  separated  from  the  beginning,  or  beyond  the 
middle,  except  in  D.  micans. 

12.     Dendroctonus  simplex  Le  Conte. 

(PI.  V,  fig.  12.) 

Adult. — Typical  female:  Length,  3.9  mm.,  dark  reddish-brown. 
Head  with  front  distinctly  convex,  with  faint  posterior  impression. 
Pronotum  with  distinctly  coarse  and  fine  punctures  intermixed;  ely- 
tral declivity  with  striae  deeply  impressed;  epistomal  process  narrow, 
flat,  the  sides  nearly  parallel,  apex  not  extending  beyond  the  anterior 
frontal  margin;  elytral  rugosities  moderately  coarse,  becoming  finer 
on  the  lateral  areas,  sparse,  coarser,  and  more  acute  on  the  dorsal 
area  and  vertex;  striae  toward  suture  impressed,  not  impressed  on 
lateral  area;  strial  punctures  coarse  and  distinct.  Pronotum  with 
moderately  long  reclining  hairs  on  lateral  area.  Secondary  sexual 
characters:  Elytral  declivity  with  interspaces  more  rugose  and  the 
striae  more  distinctly  impressed. 

.  Typical  female  labeled,  name  label,  "Hopk.  1/22/08,  IT.  S.  41,   9  , 
Grand  Ledge,  Mich.,  21.4"  ( =  April  21). 

Typical  male:  Length,  3.8  mm.;  elytra  more  shining,  less  rugose; 
declivity  shining,  interspaces  convex  and  smooth,  with  fine,  distinct 


118  THE  SCOLYTID  BEETLES. 

punctures  and  with  striae  distinctly  impressed  and  finely  punctured ; 
otherwise  as  in  female. 

,  Typical  male  labeled,  name  label,  "Hopk.  1/22/08,  H.  S.  40,    $, 
Grand  Ledge,  Mich.,  20.5"  (  -  May  20). 

Variations. — The  length  varies  from  3.5  to  5  mm.,  with  the  average 
about  4.7  mm.  The  color  varies  from  reddish  to  reddish-brown,  with 
the  head  and  thoracic  segments  ranging  from  light  to  dark  brown, 
and  nearly  black.  The  epistomal  characters  are  more  constant  in 
this  and  the  next  species,  otherwise  the  usual  variation  in  the  sculp- 
ture and  vestiture  of  the  head,  pronotum,  and  elytra  prevails.  The 
greatest  variation,  other  than  size,  is  found  in  the  punctures  of  the 
pronotum  and  in  the  strial  punctures  and  interspacial  rugosities  of 
the  elytra. 

Distinctive  characters. — The  characters  which  distinguish  this 
species  from  the  following,  to  which  it  is  more  closely  allied,  are  the 
much  smaller  average  size  of  the  individual  and  the  coarser  and 
deeper  punctures  of  the  pronotum. 

Revisional  notes. — The  original  description  was  based  on  two  male 
specimens  labeled  "  Canada,"  which  havebeen  examined  by  the  writer 
and  found  to  agree  with  the  common  species  which  lives  in  the 
eastern  larch.  The  comparison  in  the  description  with  D.  obesus 
must  refer  to  D.  pseudotsugx  Hopk.,  representatives  of  which  were 
then  confused  with  the  true  D.  obesus  (Mann.) .  The  smooth  intervals 
on  the  declivity  referred  to  is  a  male  character.  The  reference  to  a 
much  deeper  sutural  stria  relates  to  what  is  now  recognized  as 
stria  1.  The  revision  relates  to  the  type  specimens.  With  our 
present  knowledge  of  the  specific  characters,  those  given  in  Le  Conte's 
tables  are  only  partially  applicable.  It  is  evident  that  no  other 
species  were  confused  with  this  one  in  Le  Conte's  description  and 
revision,  but  it  was  involved  in  the  revision  under  D.  obesus  (1868) 
and  D.  similis  (1873).  In  1900  it  was  in  Le  Conte's  collection  under 
D.  rufipennis,  labeled  "Lake  Superior"  and  "Tex.,"  and  under 
D.  similis,  labeled  "Lake  Superior"  and  "Can."  In  Dietz's  revi- 
sion, the  specimens  from  Colorado  and  California  were  evidently 
D.  pseudotsugse,  but  did  not  involve  any  confusion  in  the  description, 
except  in  the  length,  6.2  mm.,  which  was  evidently  based  on  a 
specimen  of  D.  pseudotsugse. 

The  species  was  found  to  be  represented  in  the  Horn  collection  by 
one  specimen,  under  simplex,  labeled  "Can.,"  and  two  specimens 
under  D.  similis,  labeled  "Can." 

Pupa. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  apex  of  the  front  and  middle  femora  has  a  minute 
subapical  granule.  Abdominal  tergite  1  with  very  small  and  2  to  61 
with  stout,  prominent  pleural  spines,  1  without  dorsal  or  lateral,  2; 
without  dorsal,  3  to  6  with  prominent  dorsal  spines,  becoming  larger, 
toward  6,  2  to  6  with  two  lateral  spines  each  side,  becoming  more 


THE    (JKNt'S    DENDROCTONUS. 


119 


prominent  toward  the  latter,  7  with  two  minute  dorsal  hairs,  8 
smooth,  9  with  prominent  widely  separated  spines.  Pupal  type, 
labeled  "Hopk.  U.  S.  No.  6444b."* 

The  usual  variation  in  arrangement  and  number  of  minor  spines 
prevails,  but  the  pupa  of  this  species  is  easily  distinguishable  from 
that  of  the  foljowing  by  its  smaller  size  and  the  more  prominent 
dorsal,  lateral,  and  pleural  spines. 


FIG.  73.—Dendroctonus  simplex:  Egg  galleries  and  larval  mines.     ( Original.) 

. — In  addition  to  the  generic  and  divisional  characters,  the 
front  is  convex,  opaque,  with  the  posterior  angle  obtuse,  and  the 
middle  with  an  indistinct  transverse  elevation,  and  transversely 
rugose.  The  clypeus  is  prominent,  shining,  with  a  distinct  median 
impressed  line  and  the  apex  broadly  emarginate;  the  labium  is  short, 
with  the  apex  broadly  rounded.  The  sternellar  lobes  of  the  thoracic 
segments  are  prominent  and  with  distinct  foot  calli.  Larval  type 
labeled  uHopk.  U.  S.  No.  6444b." 

Galleries    (fig.   73).— Egg  galleries  longitudinal,  slightly  winding, 
and  sometimes  branched  and  grooved  on  the  surface  of  the  wood,  as 


120 


THE   SOOLYTID   BEETLES. 


well  as  deeply  grooved  in  the  inner  bark;  larval  mines  and  pupal 
cells  exposed  in  the  inner  bark.  Eggs  are  placed  in  groups  of  three 
to  five  or  more,  and  the  larval  mines,  which  are  short,  are  separated 
from  the  start.  The  galleries  differ  from  those  of  the  next  species 
by  their  smaller  size,  more  elongate  and  winding  form  of  the  egg 
galleries,  and  the  much  shorter  larval  galleries  arranged  in  much 
smaller  groups. 

Distribution  (fig.  74). — (Hopk.  U.  S.)  Maine:  Cupsuptic.  Michi- 
gan: Grand  Island,  Munising,  Mackinac  Island,  Seney.  (Hopk.  W. 
Va.)  West  Virginia:  Cranesville.  Additional  localities  from  other  col- 
lections: (U.S.N.M.)  Ungava  Bay,  Canada;  Agricultural  College, 
Mich.  (H.  &  S.)  Marquette,  Grand  Ledge,  and  Port  Huron,  Mich. 


FIG.  74,—Dendroctonus  simplex:  Distribution  map.    (Original.) 

(D.  A;)  West  Stewartstown,  N.  H.  One  specimen  in  the  Le  Conte 
collection  under  D.obesus,  labeled  " Texas"  (must  be  an  erroneous 
locality,  resulting  from  some  mistake) . 

Host  tree. — Larix  laricina. 

Identified  specimens. — Le  Conte,  10  specimens  (2  under  D.  simplex, 
3  under  D.  rufipennis,  and  5  under  D.  similis)',  Horn,  3  specimens 
(2  under  simplex,  2  under  similis)',  U.S.N.M.,  6;  H.  &  S.,  10;  D.A., 
5  specimens;  Hopk.,  W.  Va.,  157,  and  Hopk.  U.  S.,  over  150 
specimens. 

BIBLIOGRAPHY  AND  SYNONYMY. 

Dendroctonus  simplex.  Le  Conte,  1868,  p.  173,  original  description,  synopsis, 
localities.  Le  Conte,  1876,  p.  385,  revision,  synopsis,  bibliography,  localities. 
Packard,  1887,  p.  177  (Le  Conte  quoted).  Schwarz,  1888,  p.  175,  synonymy, 
habits  in  larch.  Packard,  1887,  p.  177,  Le  Conte  quoted.  Packard,  1890,  p.  722 


THE    GENUS    DKNDROCTONUS.  121 

(ibid).  Dietz,  1890,  p.  31  (in  part),  Michigan  and  Lake  Superior,  fig.  4,  antenna 
and  epit'toma.  Harrington,  L881,  p.  27,  habite  and  host.  Hopkins,  1898a,  [>.'.!>, 
distinct  from  rufipennis  (piixaperda).  Hopkins,  18981),  in  larch  in  W.  Va. 
Hopkins,  1899a,  p.  392,  etc.,  fig.  Iviii,  adult,  revisional  notes,  etc.,  host,  distribu- 
tion. Hopkins,  1899c,  p.  343,  good  sRecies,  habit,  host,  etc.  Felt,  1906,  p.  752 
(in  part),  bibliography. 

Dendroctonus  similis  ^not  of  Le  Conte,  1860)  Le  Conte,  1876,  p.  385  (in  part),  revi- 
sion, synonymy,  bibliography,  localities.  Dietz,  1890,  p.  31,  Canada. 

Dendroctonus  rufipennis  (not  of  Kirby)  Le  Conte,  1876,  p.  385  (in  part)  (in  collec- 
tion 1900-1907,  under  rufipennis). 

Dendroctonus  sp.     Harrington,  1884,  p.  218.     Packard,  1890,  p.  903. 

13.     Dendroctonus  pseudotsugae  Hopkins. 

(PI.  V,  fig.  13.) 

Adult. — Type  of  species:  Length  5.75  mm.;  reddish  brown,  with 
the  prothorax  darker.  Head  with  front  convex,  with  faint  median 
and  posterior  impression;  elytral  declivity  with  striae  deeply  im- 
pressed; epistomal  process  narrow,  slight,  with  sides  nearly  parallel, 
the  apex  scarcely  projecting  beyond  the  anterior  margin.  Pronotum 
with  punctures  fine,  and  moderately  regular  in  size;  elytral  rugosities 
moderately  coarse,  finer  on  lateral  area,  coarse  and  more  acute  on 
dorsal  area  and  vertex;  stria?  of  dorsal  area  distinctly  impressed,  not 
impressed  on  lateral  area;  punctures  coarse  and  distinct.  Pronotum 
with  moderately  long  hairs  on  the  lateral  area.  Secondary  sexual 
characters:  Elytral  declivity  convex,  with  interspaces  rugose  and 
the  striae  distinctly  impressed  and  punctured. 

Type  labeled  "Type  No.  7450  U.S.N.M.,"  name  label,  "Hopk. 
1/22/08,  Pseudotsuga  taxifolia,  Hopkins,  collector,  Grants  Pass,  Or., 
9  ,  Hopk.  U.  S.  39." 

Male  type:  Length  5.75  mm.;  elytral  declivity  with  interspaces 
strongly  convex  and  smooth,  shining,  sparsely  punctured;  striae 
deeply  impressed,  punctures  obscure,  otherwise  as  in  female. 

Male  type  labeled  il  $  type,"  name  label,  "Hopk.  1/22/08,"  other- 
wise same  as  female. 

Variations. — The  length  varies  from  4  to  7  mm.,  with  the  average 
about  6  mm.  The  color  ranges  from  light  reddish  to  nearly  black. 
The  usual  variation  in  sculpture,  vestiture,  etc.,  prevails.  The 
greatest  variation  is  in  the  size  and  color,  and  in  the  size  of  the 
punctures  of  the  pronotum:  The  epistomal  process  varies  consid- 
erably, so  that  in  some  specimens  it  extends  beyond  the  epistomal 
margin,  while  in  others  it  does  not. 

Distinctive  characters. — This  species  and  the  one  preceding  are 
at  once  distinguished  from  all  of  the  other  species  of  the  genus  by  the 
characters  of  the  epistoma  and  from  each  other  by  the  sculpture  of 
the  pronotum  and  the  difference  in  average  size  of  representative 
individuals.  D.  pseudotsugse  is  distinguished  especially  by  the 
shining  and  finely  punctured  pronotum. 


122 


THE   SCOLYTID   BEETLES. 


Revisional  notes. — This  species  has  been  an  element  of  much  con- 
fusion in  descriptions,  revisions,  and  identifications,  under  the 
names  D.  similis,  D.  obesus,  D.  rufipennis,  etc.  It  is  represented  in 
the  type  series  in  Le  Conte's  collection  under  D.  similis,  but  the 
specimen  which  bears  the  name  label,  and  therefore  the  type  of 
D.  similis,  is  a  true  D.  obesus  (Mann.).  Le  Conte  (1868,  p.  173)  referred 
D.  similis  to  obesus  on  account  of  the  intervals  of  the  elytra  being 
" rough  for  their  whole  extent,"  which  is  the  case  in  the  type  of 
D.  similis,  and  in  all  females  of  D.  obesus.  Later  he  evidently  com- 


FIG.  75—Dendroctonus  pscudotsugse:  Egg  galleries  and  larval  mines,  a,  Beginning  or  basal  sections  of  egg! 
galleries  in  bark;  b,  entrance;  c,  egg  gallery;  d,  ventilating  hole;  e,  egg  nest;/,  abnormal  branch;  g,  lar- 
val mines;  h,  egg  gallery  packed  with  borings;  i,  subsequent  passage  or  inner  gallery  through  borings. 
(Original.) 

pared  the  type  of  D.  similis  with  a  single  male  specimen  of  D.  olesusA 
in.  his  collection,   which,   according  to  Mr.   Henshaw,   is  from  thej 
Mannerheim  collection,  and  finding  that  this  differed  from  his  D. 
similis  in  the  smooth  elytral  declivity  he  restored  D.  similis  (Le  Conte,  | 
1876,  p.  385)  and  called  attention  to  the  roughened  interspaces  of  tl 
declivity  as  a  distinctive  character;  all  of  which  makes  it  quite  cleai 
that  he  considered  the  specimen  bearing  the  name  label  as  the  type  j 
of  his  D.  similis  and  that  therefore  this  name  must  fall  as  a  synonyi 
of  D.  obesus  Mann.     Thus  the  other  specimens  of  the  type  series  ai 
left  to  represent  a  distinct  species  as  here  described.     In  1900  it  wt 


THE   GENUS   DENDROCTONUS. 


123 


represented  in  the  LeConte  collection  by  two  specimens  labeled  "Or." 
and  three  specimens  labeled  "Van."  under  D.  similis,  and  one,  speci- 
men labeled  "Garland  Pass,  Col.,"  under  D.  rufipennis.  In  1900 
it  was  represented  in  the  Horn  collection  by  one  specimen  labeled 
"Col."  and  one  specimen  labeled  "Cal.,"  and  in  the  A.  E.  S.  collec- 
tion by  three  specimens  from  Oregon  under  D.  similis  and  two  speci- 
mens labeled  "Col."  under  D.  rufipennis.  Dietz's  revision  under 
D.  similis  (1890,  pp.  30-31)  includes  the  characters  of  D.  pseudo- 
tsugse,  as  represented  by  the  Oregon,  Colorado,  and  California  speci- 


FIG.  76—Dendroctontu  pseudotsugse:  Egg  gallery  and  larval  mines,  o,  Egg  gallery  in  bark  and  grooved 
in  surface  of  wood;  6,  larval  mines  in  bark;  c,  larval  mines  marked  and  slightly  grooved  on  surface  of 
wood.  (Original.) 

mens,  while  the  specimens  from  Canada  represented  D.  simplex,  and 
one  from  California  referred  to  in  the  note  is  D.  monticolse. 

Pupa. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  apices  of  the  front  and  middle  femora  are  smooth; 
abdominal  tergite  1  is  without  a  pleural  spine,  2  with  small,  and  3 
to  6  with  rather  stout  ones;  1  and  2  are  without  dorsal  and  lateral 
spines,  while  3  to  6  have  a  pair  of  dorsal  and  a  pair  of  lateral  ones 
each  side;  7  and  8  are  smooth,  and  9  has  the  usual  prominent  pleural 
spines.  Pupal  type  labeled  "Hopk.  U.  S.  No.  2298." 


124 


THE    SCOLYTID   BEETLES. 


The  usual  variation  in  number  a'nd  arrangement  of  minor  spines 
prevails  in  other  specimens,  but  they  are  easily  distinguished  from 
those  of  D.  simplex  by  their  larger  size  and  less  prominent  dorsal, 
lateral,  and  pleural  spines. 

Larva. — In  addition  to  the  generic  and  divisional  characters,  the 
front  is  opaque,  except  toward  the  apex,  where  it  is  more  shining, 
•and  the  apex  is  subacute;  the  middle  has  a  transversely  rugose, 

elevation,  slightly  more  ele- 
vated and  broader  toward 
the  suture.  The  clypeus  is 
prominent,  shining,  and  with 
an  impressed  line  from  the 
middle  to  the  anterior  mar- 
gin, which  is  broadly  emar- 
ginate;  labium  short,  with 
the  apex  broadly  rounded; 
the  sternellar  lobes  are  mod- 
erately prominent,  with  in- 
distinct foot  calli.  Larval 
type  labeled  "Hopk.  U.  S. 
No.  22^." 

Galleries  (figs.  75-77).— 
The  egg  gallery  is  longitudi- 
nal, short,  but  slightly  wind- 
ing, sometimes  branched, 
slightly  grooving  the  surface 
of  the  wood,  and  deeply 
grooved  in  the  inner  bark. 
The  larval  mines  and  pupal 
cells  are  exposed  in  the  inner 
bark,  and  the  eggs  are  rather 
closely  placed  in  groups  of 
three  to  ten  or  more,  but  the 
larval  mines  are  separated 
from  the  start  and  are  usu- 
ally extended  for  some  dis- 
tance from  the  egg  galley. 
The  galleries  of  this  species 
differ  from  those  of  the  one  preceding  by  their  larger  size  and  shorter 
form  of  the  egg  gallery  and  the  much  larger  larval  mines,  which  are 
arranged  in  larger  groups. 

Distribution  (fig.  78). — (Hopk.  U.  S.)  Arizona:  Chiricahua  National 
Forest,  Flagstaff,  San  Francisco  Mountains,  Santa  Catalina  National 
Forest.  California:  Fieldbrook,  Guerneyville,  McCloud,  San  Mateo 
County  (Big  Basin).  Colorado:  Colorado  Springs,  Fort  Garland,  Gun- 
nison  National  Forest,  Indian  Creek,  Leavenworth  Valley,  Moffat, 


FIG.  77.—Dendroctonus  pseudotsugx:  Section  of  log  with 
bark  removed,  showing  brood  galleries  marked  and 
grooved  on  surface  of  wood.  ( Original.) 


THE   GENUS   DENDROCTONUS. 


125 


Ouray,  Palmer  Lake,  San  Isabel  National  Forest,  San  Juan  National 
Forest,  Saguache.  Idaho:  Beaver  Canyon,  Centerville,  Bailey, 
Henrys  Lake  National  Forest,  Kooskia,  Kootenui,  Pioneerville, 
Priest  River,  Sand  Point,  Smiths  -Ferry,  Stites.  Montana:  Belton, 
Bo/eman,  Middle  Creek  (Gallatin  County),  Ovando.  New  Mexico: 
Capitan,  Cloudcroft,  Sacramento  National  Forest,  Santa  Fe;  Ver- 
mejo.  Oregon:  Corvallis,  Detroit,  Grants  Pass,  Newport,  Slate 
Creek,  St.  Helena.  Utah:  Panguitch.  Washington:  Ashford,  Buck- 
rve,  De>  Moines,  Dole,  Gray's  Harbor  City,  Hoquiam,  Junction, 
Kent,  Keyport,  Meredith,  New  London,  North  Bend,  Orting, 
Pialschie,  Port  Angeles,  Port  Williams,  Pullman,  Puyallup,  Rock 


•\-    /.*:';:•;« 


••  v      f.:::" '•••  i    •-.v.v  \   /"  /--" 

i   ;  V  ':'"  ;^;T---- •  S-^-- i j--' -y" 

X     .'  :«•  •  •  ••;•;••   •;.-  :-;:-?:.-      i                         ».          7  ,^_,- — — 

\     •   .*>   •    ••••.-.:.'       •..--•  • , -»-- '- v 


FIG.  78. — Dcndroctonus  pseudotsugse:  Distribution  map.    (Original.) 

Creek,  Satsop.  Additional  localities  from  other  collections:  (Le  Conte) 
Vancouver,  B.  C.  (U.S.N.M.)  Easton,  Wash.  ( H.  &  S.)  Hood 
River,  Oreg;  Beaver  Canyon,  Idaho.  (D.  A.)  Mount  Angel,  Oreg. 
(Soltau)  Seattle,  Wash.  (Wickham)  Leavenworth  Valley  and 
Kalispell,  Mont. 

Host  trees. — Pseudotsuga  taxifolia,  P.  macrocarpa,  and  Larix 
occidentalis. 

Identified  specimens. — Le  Conte,  6  specimens  (1  under  rufipennis, 
5  under  D.  similis);  Horn,  2;  A.  E.  S.,  5;  Dietz,  2;  U.S.N.M.,  7; 
H.  &.  S.,  2;  Soltau,  3  ;  Webb,  21;  Wickham,  2;  Laurent,  1;  D.  A.,  5; 
Hamilton,  1 ;  Hopk.  U.  S.,  over  700  specimens,  including  all  stages  and 
work. 


126  THE   SCOLYTID   BEETLES. 

BIBLIOGRAPHY  AND  SYNONYMY. 

Dendroctonus  similis  (not  of  Le  Conte,  1860)  Le  Conte,  1876,  p.  385  (in  part),  revision, 
synonymy,  bibliography,  localities.  Le  Conte,  1878,  p.  469,  listed,  Leavenworth 
Valley,  Colo.  Packard,  1887,  p.  177,  Le  Conte  quoted.  Packard,  1890,  p.  722, 
Le  Conte  quoted.  Dietz,  1890,  pp.  30-31,  from  Oregon,  California,  Colorado,  fig.  3, 
antenna,  epistoma.  Hopkins,  1899a,  p.  392,  fig.  Iviii,  adult.  Hopkins,  1899b,  pp. 
10, 11-15,  21,  22,  26,  first  records,  habits,  hosts,  etc.  Wickham,  1902,  p.  310,  list 
and  localities.  Hopkins,  1903a,  p.  61,  synonymy.  Fall,  1907,  p.  218,  in  list, 
locality. 

Dendroctonus  rufipennis  (not  of  Kirby)  Le  Conte,  1876,  p.  385  (in  part)  (in  collection 
1900-1907,  under  rufipennis}.  Le  Conte,  1878,  p.  469  (in  part).  Packard,  1887, 
pp.  177,  243  (in  part?).  Hopkins,  1899b,  p.  15,  localities,  note.  Hopkins,  1904, 
p.  19,  reference. 

Dendroctonus  simplex  (not  of  Le  Conte)  Dietz,  1890,  p.  31  (in  part),  Colorado,  Cali- 
fornia. Wickham,  1902,  p.  310  (on  Dietz's  authority). 

Dendroctonus  pseudotsugx  Hopkins,  1901b,  p.  67,  brief  description  of  adult,  galleries, 
habits,  distribution,  etc.  Hopkins,  1903a,  p.  60,  habits,  comparison  with  D.  simi- 
lis, which=D.  obesus.  Hopkins,  1905,  pp.  10,  11,  brief  description,  habits,  etc. 
Hopkins,  1906a,  p.  4,  old  work. 

Dendroctonus  n.  sp.     (Douglas  spruce  beetle.)     Hopkins,  1904,  pp.  19,  45. 

14.     Dendroctonus  piceaperda  Hopkins. 

(PI.  V,  fig.  14.) 

Adult. — Type  of  species,  female:  Length,  5.75  mm.;  elytra  red, 
thorax,  head,  and  abdomen  black;  head  with  front  convex  and  with 
faint  median  and  posterior  impression  and  anterior  elevated  line. 
Elytral  declivity  with  striae  not  deeply  impressed;  epistomal  process 
broad,  concave,  with  the  lateral  section  oblique;  punctures  of  prono- 
tum  distinctly  irregular;  posterior  half  of  proepisternal  area  not 
punctured;  elytral  striae  distinctly  impressed  in  dorsal  and  lateral 
areas,  with  punctures  rather  coarse  and  distinct;  interspaces  slightly 
convex ;  rugosities  acute,  rather  closely  placed,  irregular.  Secondary 
sexual  characters:  Declivity  convex;  striae  very  faintly  impressed, 
with  fine  indistinct  punctures;  interspaces  nearly  flat,  shining,  with  , 
approximate  row  of  fine  granules. 

Type  labeled  "Type  No.  7451  U.S.N.M.,"  name  label,  "Hopk. 
4/23/02,  compared  with  Kirby  type  rufipennis,  does  not  agree,  Picea 
canadensis,  Hopkins,  collector,  Camp  Caribou,  Me.,  9  type,  Hopk. 
U.  S.  326." 

Male  type:  Length,  5.6  mm.;  elytra  dark  reddish-brown;  thorax 
and  head  darker;  elytral  declivity  convex;  striae  not  impressed; 
punctures  obscure;  interspaces  flat,  shining,  and  finely  punctured, 
with  very  small  granules  toward  vertex. 

Type  labeled,  "  $  type,  type  of  drawing,"  name  label,  "Hopk. 
1/22/08,  Picea  canadensis,  Hopkins,  collector,  Camp  Caribou,  Me., 
$  type,  Hopk.  U.  S.  326." 

Variations. — The  length  varies  from  4.7  to  6  mm.,  with  the  average 
about  5.5  mm.  The  color  ranges  from  uniform  light  red  to  black,  to 
the  head,  thorax,  and  abdominal  sternites  dark  to  black,  with  the  ely- 


THE   GENUS   DENDROCTONUS.  127 

•bra  lighter  or  red.  The  sculpture  and  vestiture  of  the  epistoma,  front, 
pronotum,  and  elytra  vary  as  usual.  The  greatest  variation  is  in  size 
•ind  color. 

Distinctive  characters. — The  characters  which  distinguish  this  spe- 
bies  from  the  next  are  its  smaller  average  size,  slightly  less  elongate 
rorm,  less  shining  elytra,  with  the  striae  more  distinctly  impressed  on 
[the  sides  and  the  interspaces  slightly  more  convex  and  more  acutely 
•rugose.  The  difference  is  not  so  perceptible  in  comparing  single  indi- 
Ividuals  as  when  many  individuals  of  both  species  are  compared.  It 
I  differs  from  D.  borealis  by  the  noticeably  more  elongate  and  narrower 
[pronotum,  and  from  species  17  to  21  it  is  distinguished  by  the  dis- 
tinctly impressed  lateral  striae  of  the  elytra,  except  D.  punctatus  Lee., 
which  is  at  once  recognized  by  the  coarse  punctures  of  the  declivital 
striae.  It  is  at  once  distinguished  from  D.  rufipennis  (Kirby)  by  its 
smaller  size  and  coarsely  punctured  and  impressed  lateral  striae. 

Revisional  notes. — Probably  no  species  of  the  genus  has  been  in- 
volved in  so  much  confusion  as  this.  It  has  been  extensively  dis- 
cussed under  D.  rufipennis,  and  confused  in  collections  with  several 
other  species  under  this  name.  There  are  three  specimens  in  the 
Le  Conte  collection  labeled  "Anticosti,"  which  were  evidently  the 
ones  referred  to  in  his  revision  (1876,  p.  385).  There  are  also  two 
specimens  without  locality  labels,  which  may  have  been  the  ones  from 
Colorado,  while'  the  one  from  Alaska  is  here  referred  to  D.  borealis. 
The  smoother  and  more  shining  declivity  referred  to  by  Le  Conte  as  a 
distinguishing  character  relates  to  the  males  only.  It  is  represented 
in  the  Horn  collection  by  two  specimens  labeled  "  Canada,"  under 
\D.  rufipennis,  which  were  therefore  evidently  included  in  Dietz's 
revision.  It  is  also  very  probable  that  the  specimens  from  New 
Brunswick  belonged  to  this  species. 

It  is  very  evident  that  the  barkbeetle  referred  to  under  D.  rufipen- 
\nis  by  Peck,  Packard,  Hough,  and  other  authors  as  depredating 
i  on  the  spruce  of  New  Brunswick,  Canada,  New  England,  New  York, 
and  Pennsylvania  was  D.  piceaperda. 

Pupa. — In  addition  to  the  generic,  divisional,  and  subdivisional 

i  characters,  the  apices  of  the  front  and  middle  femora  are  smooth; 

abdominal  tergites  2  to  6  with  very  small  pleural  spines;  1  without 

distinct  dorsal  or  lateral  spines;  2  to  3  without  dorsal,  but  with  two 

i  small  lateral  spines  each  side;  4  to  6  with  a  pair  of  very  small  dorsal 

and  three  or  four  small  lateral  spines  each  side;  7  and  8  smooth;  9  with 

usual  pleural  spines.     Pupal  type  labeled  "Hopk.  U.  S.  377." 

The  usual  variation  in  minor  details  prevails.  It  is  distinguished 
from  the  pupa  of  D.  engelmanni  by  the  less  impressed  vertex  of  the 
head  and  the  generally  smaller  spines  and  the  absence  of  dorsal 
spines  on  the  third  abdominal  tergite. 

Larva. — In  addition  to  the  generic,  divisional,  and  subdivisional 
i  characters,  the  front  has  a  slight  transverse,  rugose  elevation  situ- 


128 


THE    SCOLYTID   BEETLES. 


ated  slightly  in  front  of  the  middle,  the  anterior  surface,  including  the 
elevation,  opaque.  The  area  behind  the  elevation  is  impressed  and 
shining;  clypeus  short,  broad,  with  median  groove  and  its  apex  sub- 
acutely  emarginate  (in  dried  specimens) ;  labrum  prominent,  its  ante- 
rior margin  sub  truncate ;  mandibles  opaque,  with  slight  dorsal  impres- 
sion or  elevation;  sternellar  lobes  of  thoracic  segments  moderately 


FIG.  7S.—Dendroctonus  piceaperda:  Egg  gallery  and  larval  mines,  a,  Egg  gallery;  6,  boring  dust  packed 
in  gallery;  c,  entrance  and  subsequent  or  inner  gallery;  d,  larval  mines.    (Author's  illustration.) 

prominent  and  with  distinct  foot  calli.  Larval  type  labeled  "Hopk. 
U.  S.  No.  318." 

The  most  distinctive  characters  are  the  opaque  mandibles  with 
moderate  impression  and  elevation,  and  the  distinctly  elevated  ante- 
rior margin  of  the  epicranium. 

Galleries  (fig.  79).— The  egg  galleries  are  short,  broad,  longitudinal,j 
grooving  the  surface  of  the  wood  and  deeply  grooved  in  the  inner 


THE   (iKNTS   DENDBOCTONUS. 


129 


bark,  the  larval  mines  exposed  and  the  pupal  cells  partially  to  entirely 
exposed.  The  eggs  are  closely  placed  in  large  groups,  and  the  larval 
mines  are  at  first  contiguous  or  nearly  so,  near  the  egg  gallery,  but 
soon  become  separated  and  when  completed  are  often  as  long  as  the 
egg  gallery  or  longer.  The  egg  galleries  differ  from  those  of  all  of  the 
species  of  subdivisions  A  and  B  in  being  very  much  broader  than  the 
ilia  meter  of  the  beetle's  body.  This  broad  groove  is  packed  with 
borings,  through  which  a  central  gallery  is  excavated  by  the  parent 
beetle  after  the  eggs  have  been  deposited. 

Distribution  (fig.  80). — (Hopk.  U.  S.)  Maine:  Beaver  Pond,  Camp 
Caribou,  Cupsuptic,  Meadows.  Michigan:  Grand  Island,  Munising. 
X<  ir  Hampshire:  Waterville.  Additional  localities  from,  specimens 


FIG.  80.—Dendroctonus  piceaperda:  Distribution  map.    (Original.) 

identified  in  other  collections:  (Le  Conte)  Anticosti,  Canada.  (Horn) 
Canada.  (U.S.N.M.,  H.  &  S.)  Isle  Koyale,  Mich.  (D.  A.)  Colebrook 
and  West  Stewartstown,  N.  H.  (Wenzel)  Ricketts,  Pa. 

It  is  evident  that  this  species  follows  the  distribution  of  the  spruce 
from  the  higher  mountains  of  central  Pennsylvania  northward  and 
eastward  into  New  York,  New  Hampshire,  Maine,  New  Brunswick, 
and  Canada,  and  westward  to  the  Lake  Superior  region. 

Host  trees. — Picea  nibens,  P.  canadensis,  and  P.  mariana. 

Identified  specimens. — Le  Conte,  3  specimens  from  Anticosti,  2  with- 
out label,  under  D.  rufipennis,  1  labeled  "X.  Y."  under  D.  punctatus 
(Mar.  11,  '07),  2  specimens  without  locality  labels  doubtfully  referred 
to  this  species;  Horn,  2  specimens  labeled  "Can.,"  under  D.  rufipen- 
nis; U.S.X.M.,  H.  &  S.,  1  specimen  labeled  "Isle  Koyale;"  Weed  and 
79980—09 10 


130  THE  SCOLYTID  BEETLES. 

Fiske,  12  specimens;  Hopk.  U.  S.,  over  300  specimens,  including  all 
stages  and  work. 

BIBLIOGRAPHY  AND  SYNONYMY. 

Hylurgus  rufipennis  (not  of  Kirby)  Peck,  1876,  pp.  283,  301,  destruction  of  spruce  in 
New  York  (evidently  the  work  of  D.  piceaperda  Hopk.).  Peck,  1879,  pp.  32-38, 
ravages  in  spruce  in  northern  wilderness  (same  as  1876?).  Packard,  1890,  pp.  814- 
815  (quotes  Peck,  ibid.).  Hough,  1882,  pp.  259-263,  insect  ravages  in  spruce 
forests  of  Maine. 

Dendroctonus  rufipennis  (not  of  Kirby)  Le  Conte,  1876,  p.  385,  revision,  synopsis, 
localities.  Lintner,  1885,  p.  54,  destruction  of  spruce  in  New  York.  Fletcher, 
1887,  pp.  39-40,  habits.  Dietz,  1890,  p.  30  (in  part),  Canada  and  New  Brunswick. 
Packard,  1887,  pp.  177-243  (in  part).  Packard,  1890,  p.  722  (in  part),  quotes 
Le  Conte.  Harvey,  1898,  p.  176,  depredations  on  spruce  in  Maine;  p.  98,  host, 
distribution,  etc.  Hopkins,  1898a,  p.  69,  distinct  from  simplex.  Weed  and  Fiske, 
1898,  pp.  67-69,  report  on  investigations.  Chittenden,  1898,  p.  96,  doubt  as  to 
Kirby's  species.  Smith,  1899,  p.  364,  Lakewood,  N.  J.  Hopkins,  1899a,  pp.  349- 
393  (in  part),  reference.  Hopkins,  1899c,  p.  343  (in  part?),  reference.  Chitten- 
den, 1899,  p.  56  (in  part?),  reference.  Johnson,  1901,  p.  92,  habits  in  Pa. 
Hopkins,  1905,  p.  6,  reference  to  wrong  determination.  Felt,  1906,  p.  753  (in 
small  part),  bibliography. 

Polygraphus  rufipennis  (not  of  Kirby)  Packard,  1890,  p.  721,  [fig.  251=Polygraphus 
rufipennis  (Kirby)],  Le  Conte  quoted  (includes  several  species). 

Xyloterus  bivittatus  (not  of  Kirby)  Packard,  1890, p.  823,  fig. 276  (in part), adult?;  PI. 
XXIV,  fig.  1,  larva?,  1  a,  pupa?,  destruction  of  spruce. 

Barkbeetles.  Packard,  1890,  pp.  811-824  (in  part),  destruction  of  spruce,  New  Bruns- 
wick to  New  York. 

Dendroctonus  (Polygraphus)  rufipennis  (not  of  Kirby)  Gary,  1900,  pp.  52-54,  depre- 
dations on  spruce,  methods  of  control. 

Dendroctonus  piceaperda  Hopkins,  1901a,  p.  16,  PI.  II,  larvae,  pupae,  adult,  etc., 
original  description,  different  stages  and  galleries,  with  full  account  of  habits,  host, 
natural  enemies,  methods  of  control,  etc.  (see  also  index  and  Pis.  I-V,  XIV,  XV). 
Hopkins,  1902b,  p.  21,  mention.  Hopkins,  1902a,  p.  3.  Hopkins,  1902c,  p.  22, 
habits,  etc.  Hopkins,  1903b,  pp.  266,  270,  281,  PL  XXVII,  figs.  23-25,  stages 
and  work  figured,  revised  account  of  habits,  life  history,  methods  of  control,  etc. 
Hopkins,  1904,  p.  26,  PL  I,  fig.  3,  Pis.  V,  XII,  fig.  1,  Pis.  XIII,  XIV,  XV,  stages 
and  work  (reprints),  habits,  hosts,  distribution,  etc.  Hopkins,  1905,  pp.  10,  11, 
distinctive  characters,  brief.  Felt,  1905,  pp.  6,  7,  habits  and  work.  Felt,  1906, 
pp.  379-385,  fig.  85  6,  history,  habits,  etc.  Hopkins,  1908,  pp.  160-161,  depreda- 
tions. 

15.     Dendroctonus  engelmanni  n.  sp. 

Adult. — Type  of  species,  female:  Length  6.2  mm.,  black.  Head 
with  front  convex,  faint  median  and  posterior  impression  and  faint 
anterior  line.  Elytral  declivity  with  striae  not  deeply  impressed; 
punctures  of  pronotum  distinctly  irregular;  posterior  half  of  proepi- 
sternal  area  not  punctured ;  punctures  of  prothorax  and  elytra  rather 
coarse;  striae  moderately  impressed;  interspaces  moderately  convex, 
and  scarcely  rugose,  except  on  dorsal  area.  Secondary  sexual  char- 
acters: Declivity  convex;  striae  rather  distinctly  but  not  deeply 
impressed ;  punctures  distinct ;  interspaces  with  rows  of  granules. 


THE   GENUS   DENDROCTONUS.  131 

Type  labeled  "Type  No.  7452  U.S.N.M.,"  name  label,  "Hopk. 
1/22/08,  Picea  engelmanni,  Capitan,  N.  M.,  W.  F.  Fiske,  collector, 
?,  Hopk.  U.  S.  3958." 

Male  type:  Length  5.5  mm.  Front  without  anterior  line.  Elytra 
with  striae  less  distinctly  impressed  and  interspaces  less  convex  than 
in  female:  declivity  convex,  with  strise  and  strial  punctures  obscure; 
interspaces  flat,  shining,  finely  but  distinctly  punctured  and  without 
granules  except  on  vertex. 

Type  labeled,  "  $  type,"  name  label,  "Hopk.  1/22/08,  Picea  engel- 
manni, Capitan,  X.  M.,  W.  F.  Fiske,  collector,  $',  Hopk.  U.  S.  3958." 

Variations. — The  length  varies  from  5  to  7  mm.,  with  the  average 
at  about  6.5  mm.  The  color  ranges  from  uniform  light  to  dark  red 
and  black,  to  black  head,  thorax,  and  abdomen,  and  red  elytra.  The 
sculpture  ami  vest  it  lire  of  the  epistoma  vary  as  usual,  with  the 
greatest  variation  in  size,  color,  and  punctures. 

Distinctive  characters. — The  characters  which  serve  to  distinguish 
this  species  from  the  one  preceding  are  the  larger  average  size, 
slightly  more  elongate  form,  more  shining  elytra,  with  the  lateral 
strijp  somewhat  less  impressed,  the  punctures  usually  coarser,  and  the 
interspaces  less  acutely  rugose.  It  is  more  closely  allied  to  D.  obesus, 
from  which  it  is  distinguished  by  the  commonly  darker  prothorax, 
and  more  distinctly  impressed  lateral  strise  of  the  elytra,  with  coarser 
punctures. 

Revisional  notes. — This  species,  like  the  preceding,  has  been  involved 
in  the  confusion  in  revisions  and  collections  under  D.  rufipennis. 
The  species  under  this  name  was  represented  in  the  Le  Conte  collec- 
tion by  two  specimens  labeled  "Alta,  Ut."  and  "Colo.,"  by  two  in 
Horn's  collection  labeled  "H.  B.,"  and  "Alta,  Ut.,"  and  by  one 
specimen  from  Doctor  Dietz,  labeled  "Ut."  These  were  doubtless 
involved  in  Le  Conte 's  and  Dietz's  revisions. 

Pupa. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  apices  of  the  front  and  middle  femora  are  smooth;  ab- 
dominal tergites  2  to  6  with  small  pleural  spines;  1  and  2  without 
dorsal  but  with  lateral  spines,  and  3  to  6  with  dorsal  and  lateral  spines; 
7  and  8  smooth;  9  with  pleural  spines,  as  usual.  Pupal  type  labeled 
"Webb  Xo.  2." 

The  usual  variation  in  minor  details  prevails,  but  the  pupa  of  this 
species  is  distinguished  from  that  of  the  preceding  one  by  the  more 
distinctly  impressed  vertex  of  the  head,  the  generally  coarser  spines, 
and  the  presence  of  dorsal  spines  on  the  third  abdominal  tergite. 

Larva. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  front  has  a  transverse  rugose  elevation  situated  near 
the  middle;  the  anterior  surface,  including  the  elevation,  is  opaque; 
the  area  behind  the  elevation  is  impressed  and  shining,  clypeus 


132 


THE   SCOLYTID   BEETLES. 


broad,  with  median  dorsal  groove  and  the  apex  subacutely  emar- 
ginate;  labrum  prominent,  its  anterior  margin  truncate;  mandibles 
opaque  toward  base,  more  shining  toward  apex,  with  a  distinct  dorsal 
impression  and  oblique  ridge  near  the  middle;  sternellar  lobes  of  the 
thoracic  segments  moderately  prominent  and  with  distinct  foot  calli. 
t  Larval  type  labeled  "Webb 

No.  2." 

The  most  distinctive  charac- 
ters separating  the  larva  of  this 
species  from  that  of  the  preced- 
ing one  are  the  more  shining 
mandibles,  with  much  deeper 
dorsal  impression  and  more 
prominent  oblique  ridge  and 
the  much  less  distinctly  ele- 
vated anterior  margin  of  the 
epicranium. 

Galleries  (fig.  81).— The  gal- 
leries of  this  species  are  very 
much  the  same  as  those  of  the 
preceding  one,  except  that  the 
larval  mines  are  more  distinctly 
contiguous  for  a  greater  dis- 
tance from  the  egg  galleries. 
Distribution  (fig.  82). — 
(Hopk.  U.  S.)  Arizona:  Chiri- 
cahua  Mountains.  Colorado: 
Clyde,  Boulder,  Craig,  Fort  Col- 
lins, Glenwood  Springs,  Gunni- 
son,  Hahn's  Peak,  Holy  Cross 
National  Forest,  Meeker,  Ou- 
ray  National  Forest,  Sun  Isabel 
National  Forest,  Steamboat 
Springs,  White  River  National 
Forest.  Neiu  Mexico:  Capi- 
tan  Mountains,  Sierra  Blanca 
Mountains,  Sacramento  Na- 
tional Forest.  South  Dakota: 
Spearfish  Canyon,  Black  Hills. 
Utah:  Ephraim.  Wyoming:  En- 
campment. Additional  localities  from  specimens  in  other  collec- 
tions:  (Horn)  "H.  B."  (Northwest  Territory,  probably  in  Macken- 
zie River  region)  and  Alta,  Utah.  (Wickham)  Argentine,  Leadville, 
and  Silver  Plume,  Colo.  (Cockerell)  Las  Vegas,  N.  Mex.  (H.  &  S.) 
Calgary,  Alberta;  Glacier,  British  Columbia.  (Webb)  Collins,  Idaho. 


FIG.  81.—Dendroctonus  engelmanni:  Egg  gallery  in  liv- 
ing bark.  A,  Normal;  B,  boring  dust  removed;  a, 
entrance;  6,  basal  section;  c,  boring  dust  packed  in 
gallery;  d,  subsequent  or  inner  gallery;  e,  venti- 
lating burrow;/,egg  nest,  with  and  \vithouteggs;  g, 
freshly  hatched  larvte;  h,  pits  in  roof  of  gallery. 
(Original.) 


THE   GENUS   DENDROCTONUS. 


133 


Host  trees. — Picea  engelmanni  and  7>.  canadensis. 

Identified  xjHrintcns. — Le  Conte  collection,  2  specimens;  Horn,  2; 
Diet/,  1  (Utah);  U.S.N.M.  (II.  &  S.),  4;  Wickham,  4;  CockereU,  7; 
Webb,  25;  Ilopk.  U.  S.,  more  than  200  specimens,  including  all 
stages  and  work. 


FIG.  S2.—Dcndroctonus  engelmanni:  Distribution  map.    (Original.) 

BIBLIOGRAPHY  AND  SYNONYMY. 

Dendroctonus  rufipennis  (not  of  Kirby)  Le  Conte,  1876,  p.   385,  revision  (?).     Le 

(.'onto,   1878,  p.  469    (in  part)  (in  collection  1900-1907,  under  D.  rufipennis}. 

Packard,  1887,  pp.  177-243  (in  part).     Packard,  1890,  p.  721  (in  part),  p.  722  (in 

part),  quotes  Le  Conte.     Dietz,  1890,  p.  30,  Colorado,  Utah.     Wickham,  1902,  p. 

309,  list,  localities. 

Dendroctonus  dietzi  Hopkins,  1902a,  manuscript  name  only  for  variation  (Utah). 
it-ton  n.^  californicus  Hopkins,  1902a,  p.  3,  manuscript  name  only,  locality. 
D<  iidroctonus  wickhanii  Hopkins,  1902a,  p.  3,  manuscript  name  only. 
I)< mlroctonus  piceaperda  (not  of  Hopkins)   Wickham,  1902,  p.  310,  in  list,  locality, 

host,  reference  to  synonymy.     Hopkins,  1906a,  pp.  4,  5,  old  work  on  Pike's  Peak. 
Dendroctonus  piceaperda  var.  engelmanni  (Hopk.)  Fall,  1907,  p.  218,  manuscript  name, 

list,  localities. 
Dendroctonus  piceaperda  (not  of  Hopkins)  var.     Fall,  1907,  p.  218,  list,  Cloudcroft, 

X.  Mrx. 
Tin1  Engelmann  spruce  beetle.     Hopkins,  1908,  pp.  161-162,  depredations. 

16.     Dendroctonus  borealis  n.  sp. 

(PL  V,  fig.  16.) 

Adult.— Type  of  species,  female:  Length  6  mm.,  nearly  black. 
Ileud  with  front  convex,  with  faint  anterior  and  posterior  impressions 
and  faint  anterior  line;  elytral  declivity  with  striae  not  deeply  im- 


134 


THE   SCOLYTID   BEETLES. 


pressed;  punctures  of  pronotum  distinctly  irregular;  posterior  half 
of  proepisternal  area  not  punctured;  punctures  of  pronotum  and 
elytra  moderately  coarse;  elytra!  striae  scarcely  impressed  except  in 
dorsal  area;  interspaces  scarcely  coarser  -and  but  faintly  rugose, 
except  toward  base  and  vertex.  Secondary  sexual  characters :  Elytral 
declivity  convex;  striae  faintly  impressed,  with  punctures  moderately 
distinct;  interspaces  slightly  convex,  with  distinct  row  of  granules. 

Type  labeled  "Type  No.  7453  U.S.N.M.,"  name  label,  "Hopk. 
1/22/08,  U.S.N.M.  22,  Alaska,  9  ,  U.S.N.M.  Ace.  25431." 

Male  type:  Length  6  mm.,  elytra  red;  thorax,  head,  and  abdomen 
much  darker;  other  characters  the  same  as  in  female,  except  elytral 
declivity,  which  is  shining,  the  striae  and  strial  punctures  obscure; 


FIG.  83.—Dendroctonus  borcalis:  Distribution  map.    (Original.) 

interspaces  flat,  shining,   and  1  and  2  without  granules  except  toward 
vertex. 

Male  type  labeled  "type  of  drawing,"  "  $  type,"  name  label, 
"Hopk.  1/22/08,  Picea  canadensis,  Eagle,  Alaska,  W.  H.  Osgood, 
collector,  $  ,  Hopk.  U.  S.  1170a." 

Variations. — There  is  scarcely  any  variation  in  the  four  specimens 
in  the  collections,  but  the  color  varies  from  nearly  black  in  the  type 
to  the  head,  thorax,  and  abdomen  dark,  and  the  elytra  red  in  the  other 
specimens. 

Distinguishing  characters.— The  short,  stouter  form,  short  and  broad 
pronotum,  with  the  punctures  more  uniform  in  size,  the  punctures  of 
the  dorsal  striae  of  the  elytra  finer  and  less  distinct,  serves  to  distin-  ! 
guish  this  species  from  all  of  the  allied  forms.  It  appears  to  be  more 
closely  allied  to  D.  obesus,  but  is  distinguished  from  it  by  its  shorter 
pronotum  and  elytra,  and  the  other  characters  mentioned. 


THE   GENUS   DENDROCTONUS.  135 

Revisional  notes. — It  is  quite  evident  that  the  specimens  described 
by  Mannerheim(1853,  p.  238)  under  D.  rujipennis  are  D.  borealis.  The 
single  specimen  in  Le  Conte's  collection  under  D.  rujipennis,  labeled 
".Hylurgus  rujipennis  Kirby,"  and  locality  Kenai,  is  evidently  from 
Mannerheim's  collection,  and  probably  one  of  the  specimens  before 
him  when  he  prepared  his  description  under  that  name.  Superfi- 
cially, this  specimen  resembles  D.  piceaperda,  which  led  Le  Conte  to 
identify  his  Anticosti  and  Canada  specimens  as  D.  rujipennis,  and  is 
evidently  the  one  which  represented  the  Alaska  locality  in  his  revi- 
sions (1868  and  1876). 

The  immature  stages  and  galleries  of  this  species  have  not  been 
observed. 

Host  tree. — Picea  canadensis. 

Distribution  (fig.  83). — Alaska:  Eagle,  (?)  Kenai  Peninsula. 

Identified  specimens. — Le  Conte,  1  specimen;  U.S.N.M.,  2;  Hopk. 
U.  S.,  2,  collected  by  W.  H.  Osgood,  of  the  Biological  Survey,  U.  S. 
Department  of  Agriculture,  at  Eagle,  Alaska,  August,  1903,  from 
white  spruce. 

BIBLIOGRAPHY  AND  SYNONYMY. 

Hylurgus  rujipennis  (not  of  Kirby).  Mannerheim,  1853,  p.  —  (in  part). 
Dendroctonus  rujipennis  (not  of  Kirby).  Le  Conte,  1868-1876  (in  part). 
Dendroctonus  borealis  Hopkins,  1902a,  p.  3,  manuscript  name  only. 

17.     Dendroctonus  obesus  (Mannerheim). 

(PI.  VI,  fig.  17.) 

Adult. — Typical  female :  Length  6.5  mm.,  nearly  black.  Head  with 
front  convex,  with  faint  anterior  and  posterior  impression  and  mod- 
erately distinct  anterior  line.  Elytral  declivity  with  striae  not  deeply 
impressed;  punctures  of  pronotum  distinctly  irregular;  posterior  half 
of  proepisternal  area  not  punctured;  punctures  of  pronotum  and 
elytra  moderately  coarse;  elytral  striae  scarcely  impressed;  inter- 
spaces flat,  finely,  sparsely  rugose  on  dorsal  area  and  toward  base  of 
vertex.  Secondary  sexual  characters:  Declivity  convex,  subopaque; 
striae  faintly  impressed,  with  punctures  moderately  distinct;  inter- 
spaces faintly  convex,  with  distinct  row  of  granules. 

Typical  female  labeled,  name  label,  "Hopk.  1/22/08,  Picea  sitch- 
ensis,  Queen  Charlotte  II.,  Keen  [collector],  9  ." 

Typical  male:  Length  6.7  mm.,  black.  Front  convex,  with  faint 
anterior  impression  and  distinct  anterior  line.  Agrees  with  female, 
excepting  that  the  punctures  of  elytral  striae  and  interspacial  rugosi- 
ties are  coarser;  declivity  subopaque;  strial  impressions  and  punc- 
tures obscure;  interspaces  flat,  faintly  punctured,  and  with  a  few 
granules  toward  vertex;  pronotum  with  distinctly  elevated  line. 

Typical  male  labeled,  name  label,  "  1/22/08,  Picea  sitchensis,  Queen 
Charlotte  II.,  J.  H.  Keen,  Collr.,  $ ." 


136  THE  SCOLYTID  BEETLES. 

Variations. — The  length  varies  from  6  to  7  mm.,  with  the  average 
about  6.5  mm.  The  color  ranges  from  uniform  light  red  to  brown  in 
young  specimens,  to  uniform  black  in  matured  ones,  it  being  exceed- 
ingly rare  to  find  examples  with  the  pronotum  darker  than  the  elytra, 
which  is  so  characteristic  in  the  three  preceding  species.  The  sculp- 
ture and  vestiture  of  the  epistoma,  front,  pronotum,  and  elytra  vary 
as  usual.  The  greatest  variation  is  in  the  punctures  of  the  pronotum 
and  in  the  presence  and  absence  of  the  dorsal  line;  the  presence  or 
absence  of  a  frontal  carina  is  also  an  important  variation,  and  in  some 
examples  the  body  is  noticeably  more  elongate  than  in  others. 

Distinctive  characters. — The  characters  which  serve  to  distinguish 
this  species  from  the  three  preceding  are  the  uniform  black  color  of 
the  matured  adults  and  the  prevailingly  less  impressed  elytral  striae, 
especially  those  of  the  lateral  area,  and  also  the  prevailing  slightly 
more  elongate  form.  Its  host  tree  and  distribution  also  serve  as 
distinguishing  characters,  except,  perhaps,  in  the  case  of  borealis, 
which  may  be  found  in  the  Sitka  spruce. 

Revisional  notes. — There  can  be  little  or  no  doubt  that  the  material 
under  observation  represents  Mannerheim's  species,  whose  varieties 
a,  b,  and  c  were  evidently  immature  specimens.  D.  similis  Lee.  is 
to  be  referred  to  this,  which  fact  was  recognized  by  Le  Conte  in  his 
1868  paper,  but  the  beetle  was  subsequently  confused  with  the 
species  discussed  in  the  present  paper  under  D.  pseudotsugx.  D.  obesus 
is  represented  in  the  Le  Conte  collection  by  two  specimens,  one 
specimen  from  Mannerheim's  collection,  labelled  D.  obesus  ("  Speci- 
men 5"  under  D.  rufipennis  in  1900),  and  one  specimen,  the  type 
of  D.  similis.  It  is  possible  that  "  specimen  2"  under  D.  rufipennis 
is  also  D.  obesus,  but  was  not  recognized  by  the  writer  when  ex- 
amined in  1900.  Dietz,  1890,  did  not  recognize  or  mention  D.  obesus, 
and  it  was  not  found  by  the  writer  in  the  Horn  collection  or  that  of 
the  Academy  of  Natural  Sciences. 

Pupa. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  apices  of  the  front  and  middle  tibiae  are  smooth  or 
rarely  with  a  single  granule,  abdominal  tergites  2  to  6  with  very 
small  pleural  spines,  1  without  dorsal  but  with  small  lateral  spines, 
and  2  to  6  with  dorsal  and  lateral  ones,  7  and  8  smooth,  9  with 
prominent  pleural  spine  as  usual.  Pupal  type  labeled  "Hopk.  U.  S. 
No.  4049a." 

The  usual  variation  in  minor  details  prevails,  but  the  pupa  of 
this  species  is  distinguished  from  that  of  the  three  preceding  by  the 
more  evident  lateral  spines  of  the  first  abdominal  tergite  and  the 
prevailing  darker  tips  to  the  abdominal  spines. 

Larva. — In  addition  to  the  generic,  divisional,  subdivisional,  and 
sectional  characters,  the  front  has  a  faint  transverse  elevation  dis- 


THE   GENUS   DENDROCTONUS. 


137 


tinctly  in  front  of  the  middle  and  the  pronotal  area  is  flat  to  apex. 
The  clypeus  is  short  and  l>n>ud,  with  an  anterior  dorsal  gr<> >\e  and 
the  apex  broadly  emarginate,  lahium  prominent,  slightly  longer  than 
the  elypeus,  with  the  apex  broadly  rounded.  Larval  types,  labeled 
"Hopk.  U.  S.  Nos.  4081,  4046a,  and  4049a." 

The  most  distinctive  characters  appear  to  be  the  anteriorly  j  lac:>d 
transverse  elevation  of  the  front ;  the  characters  of  the  mandibles  and 
anterior  margin  of  the  epicranium  more  nearly  approach  those  found 
D.  engelmanni. 

latteries. — The  galleries  of  this  species   are  of  the  same,   or  of 
dlar  character  to  those  of  D.  piceaperda,  as  given  in  divisional, 


FIG.  84. — Dendroctonus  obesus:  Distribution  map.    (Original.) 

subdivisional,  or  sectional  characters,  but  differ  in  the  more  extended 
common  larval  chamber  which  precedes  the  independent  larval 
mines  which  are  usually  so  confused  by  crossing  each  other  that  they 
are  difficult  to  follow. 

Distribution  (fig.  84). — (Hopk.  U.  S.)  Oregon:  Newport.  Wash- 
ington: Hoquiam,  Aberdeen.  Additional  localities  from  other  col- 
lections: (U.S.X.M.)  (H.  &  S.)  Vancouver,  British  Columbia;  (Rev. 
Keen)  Queen  Charlotte  Islands,  British  Columbia. 

Host  tree. — Picea  sitchensis. 

Identified  specimens. — Le  Conte  collection,  2  specimens :  U.S.N.M., 
1  from  Doctor  Fletcher;  H.  &  S.,  3;  Hopk.  U.  S.,  more  than  120 
specimens,  including  all  stages. 


138  THE   SCOLYTID   BEETLES. 

BIBLIOGRAPHY  AND  SYNONOMY. 

Hylurgus  obesus «  Mannerheim,  1843,  p.  296,  original  description.  Mannerheim, 
1852,  p.  356,  spec.  474,  list,  variety  b  and  variety  c,  brief  descriptions.  Man- 
nerheim, 1853,  p.  238,  separate  p.  146,  list,  var.  d  described.  Le  Conte,  1868, 
p.  173,  mentioned,  synonymy. 

Dendroctonus  similis  Le  Conte,  1860,  p.  59,  description  (from  one  specimen  which  = 
D.  obesus}.  Le  Conte,  1868,  p.  173,  mentioned  as  synonymous  with  D.  obesus  Mann. 
Hopkins,  1902a,  p.  3,  recognized  as  synonymous  with  D.  obesus  (Mann.). 

Dendroctonus  obesus  (Mann.)  Le  Conte,  1868,  p.  173  (in  part).  Chapuis,  1869,  p.  35; 
1873,  p.  243,  revised  description.  Hamiltom,  1894,  p.  35  (in  part).  Hopkins, 
1899b,  pp.  15,  21,  habits,  host,  etc.  Schwarz,  1900a,  p.  537,  author's  reprint  p. 
185  (in  part),  list.  Hopkins,  1902a,  p.  3,  species  recognized  as  distinct  from  D. 
rufipennis  Kirby.  Hopkins,  1902c,  p.  22,  habit  and  host.  Hopkins,  1903a,  p. 
60,  reference. 

Dendroctonus  rufipennis  (not  of  Kirby).  Le  Conte,  1868,  p.  173  (?=D.  obesus). 
Le  Conte,  1876,  p.  385,  revision,  synonymy,  bibliography,  localities  (in  collection 
1900-1907,  under  rufipennis).  Packard,  1887,  pp.  176,  243  (in  part?). 

Dendroctonus  rufipennis  (obesus  Mann.)  Harrington,  1890,  p.  189,  author's  extra,  p.  19. 

Dendroctonus  keeni  Hopkins,  1902a,  p.  3,  manuscript  name  only  on  variation. 

Dendroctonus  fietcheri  Hopkins,  1902a,  p.  3,  manuscript  name  only  on  variation. 

18.     Dendroctonus  rufipennis  (Kirby). 

(PI.  VI,  fig.  18.) 

Adult. — Typical  female:  Length  6.2  mm.  Elytra  red;  thorax, 
head,  and  abdomen  reddish  brown.  Head  convex,  with  faint  ante- 
rior and  posterior  impression  and  short  anterior  line;  elytral  declivity 
with  striae  not  deeply  impressed;  punctures  of  pronotum  distinct, 
irregular;  posterior  half  of  proepisternal  area  punctured;  striae  of 
elytral  declivity  with  fine  punctures ;  elytral  striae  scarcely  impressed, 
except  toward  suture;  strial  punctures  moderately  coarse;  inter- 
spaces with  rugosities  moderately  coarse,  sparse,  and  acute;  pronotal 
punctures  coarse,  deep,  moderately  dense.  Secondary  sexual  char- 
acters: Elytral  declivity  convex;  striae  faintly  impressed;  punctures 
obscure;  interspaces  faintly  convex,  with  row  of  fine  granules. 

Typical  female  labeled  "type  of  drawing,"  name  label,  "Hopk., 
4/25/02.  Agrees  with  Kirby's  type,  compared  by  C.  O.  Waterhouse, 
H.  S.  28,  9  ,  White  Fish  Point,  Lfake]  Superior]." 

Typical  male:  Length  6.7  mm.  Elytra  dark  red,  thorax  and  head 
reddish  brown.  Agrees  with  female,  excepting  that  the  elytral 
declivity  is  more  shining,  the  strial  punctures  are  less  distinct,  and  the 
interspaces  have  less  distinct  rows  of  granules. 

Typical  male  labeled,  name  label,  "Hopk.  1/22/08,  Pinus  strobus, 
Grand  Island,  Mich.,  W.  F.  Fiske,  collector,  c? ,  Hopk.  U.  S.  3761." 

Variations. — The  length  varies  from  5  to  7.3  mm.,  with  the  average 
at  about  6.5  mm.,  the  head,  thorax,  and  ventral  segments  from 

a  This  was  Eschscholtz's  manuscript  name,  published  in  Dejean  Cat.,  3me.  Edit., 
p.  331,  but  Mannerheim  published  the  first  description. 


THE   GENUS  DENDROCTONUS.  139 

darker  reddish  brown  to  nearly  black,  while  the  elytra-  are  light  to 
dark  red.  The  greatest  variation  noted  in  the  few  specimens  under 
observation  is  in  si/e,  with  less  variation  in  sculpture  and  vestitnre 
than  in  the  preceding  species,  \os.  14,  1,">,  and  17. 

Distinctive  characters. — The  characters  which  serve  to  at  once  dis- 
tinguish this  species  from  the  preceding  allied  ones  are  the  coarse 
punctures  of  the  posterior  section  of  the  proepisternal  area,  the  more 
distinctly  red  elytra,  the  bright-red  hairs,  and  the  much  less  distinctly 
impressed  elytral  striae  of  the  lateral  area. 

Eevisional  notes. — There  is  quite  extensive  literature  under  the 
name  Ilylurgus  rufipennis  Kirby  and  Dendroctonus  rujipennis  Kirby. 
Apparently  no  part  of  it  except  the  original  description  refers  to 
Kirby's  species,  and  even  the  type  series  in  the  British  Museum  repre- 
sents at  least  one  other  species.  It  appears  that  up  to  the  fall  of  1906 
the  only  representative  of  the  species  in  the  collections  of  this  country 
was  a  female  specimen  in  the  Hubbard  &  Schwarz  collection,  U.  S. 
National  Museum,  labeled  "White  Fish  Point,  L.  S."  This,  with  other 
specimens  of  the  Dendroctonus  of  the  U.  S.  National  Museum  and  Hub- 
bard  &  Schwarz  collections,  was  submitted  to  the  writer  in  December, 
1898,  for  study,  and  was  then  labeled  "H.  S.  28."  In  1900  this  speci- 
men, together  with  another  labeled  "H.  B."  (Northwest  Territory) 
from  the  National  Museum  collection,  and  some  specimens  collected 
by  the  writer  from  the  spruce  in  Maine,  were  sent  to  the  British 
Museum  for  comparison  with  Kirby's  type  of  D.  rujipennis.  They 
were  compared  by  Mr.  Charles  O.  Waterhouse  who,  in  a  letter  dated 
November  1,  1900,  wrote  as  follows: 

I  have  examined  your  species,  but  am  only  concerned  with  your  two  largest  speci- 
mens. We  have  three  of  the  specimens  which  Kirby  had  before  him,  all  marked 
exactly  alike.  The  one  to  which  he  attached  his  ticket  is  a  dark-brown  variety  (unless 
it  is  stained  with  grease),  but  in  all  other  respects  agrees  with  your  H.  S.  28,  with 
fairly  equally  distributed  punctuation  on  the  thorax.  Kirby's  two  other  specimens 
have  red  elytra  and  agree  with  your  H.  B.  7401,  824,  and  have  a  closely  punctured 
impression  or  flattening  at  the  base  of  the  thorax. 

The  specimen  in  the  type  series  which  bore  the  name  label  when  the 
comparison  was  made  should  be  recognized  as  the  type.  Thus  it  is 
quite  certain  that  our  H.  S.  28  from  White  Fish  Point,  Lake  Superior, 
is  a  true  representative  of  the  species,  while  the  two  other  specimens 
with  which  our  H.  B.  7401,  824,  etc.,  agree  evidently  represent  D.  en- 
gelmanni  and  are  probably  the  specimens  referred  to  by  Kirby  as 
coming  from  Lat.  65°.  The  writer  is  informed  by  Mr.  Schwarz  that 
our  H.  B.  (No.  7401)  specimen  came  from  about  the  same  latitude. 
The  other  specimens  from  Maine,  which  were  so  different  from  the 
type  as  to  be  at  once  recognized  as  distinct,  were  representatives  of 
D.  piceaperda  Hopk. 

The  pupae,  larvse,  and  galleries  have  not  been  observed. 


140 


THE    SCOLYTID   BEETLES. 


Distribution  (fig.  85). —  Michigan:  White  Fish  Point  and  Grand: 
Island. 

Host  tree. — Pinus  strobus. 

Identified  specimens. — U.S.N.M.,H.  &  S.,  1  specimen;  Hopk.  U.  S.,  I 
14  specimens  of  adults,  collected  by  W.  F.  Fiske  at  Grand  Island,  Mich. ! 

BIBLIOGRAPHY. 

Hylurgus  rufipennis  Kirby,  1837,  p.  195,  No.  261,  original  description.  Packard, ! 
1887,  p.  176,  note.  Hopkins,  1899c,  p.  343  (in  part?).  Schwarz,  1900a,  p.  537, ; 
author's  copy,  p.  185  (in  part?).  Hopkins,  1901a,  p.  16,  reference  to  distribution,  | 
characters,  first  time  recognized  since  description. 


FIG.  85.—Dendroctonusrufipcnnis:  Distribution  map.    (Original.) 
19.     Dendroctonus  murrayanaB  n.  sp. 

Adult. — Type  of  species,  female:  Length,  6.9  mm;  elytra  red;* 
thorax, head,  and  abdomen  nearly  black.  Head  convex,  with  obscure 
impression;  elytral  declivity  with  striae  not  deeply  impressed;  punc- 
tures of  pronotum  distinct,  coarse,  irregular;  posterior  half  of  pro- 
episternal  area  punctured;  striae  of  elytral  declivity  with  fine 
punctures;  elytral  striae  scarcely  impressed;  punctures  moderately 
coarse;  interspaces  with  rugosities  moderately  coarse,  acute,  and 
rather  coarsely  placed;  pronotal  punctures  coarse,  deep,  moderately 
dense.  Secondary  sexual  characters:  Elytral  declivity  convex; 
striae  distinctly  impressed;  punctures  obscure;  interspaces  convex, 
with  irregular  punctures  and  rows  of  granules. 

Type  labeled  "No.  7454  U.S.N.M.,"  name  label,  "Hopk.  1/22/08, 
Pinus  murrayana,  Keystone,  Wyo.,  J.  L.  Rebmann,  collector,  9 , 
Hopk.  U.  S.  2690." 


THE   GENUS   DENDROCTONUS. 


141 


Male  type:  Length,  6.5  mm.  Agrees  with  female,  except  that  the 
elytral  declivity  is  more  shining  and  the  interspaces  are  more  dis- 
tinctly punctured  and  loss  rugose. 

Typo  labeled  "  $  type,"  otherwise  same  as  female. 

Variations. — The  length  varies  from  5.4  to  6.5mm.,  with  the  aver- 
frge  about  6  mm. 5  the  head,  thorax,  and  ventral  segments  are  dark 
reddish  brown  to  black,  while  the  elytra  are  light  to  dark  red.  The 
greatest  variation  noted  in  the  few  specimens  under  observation  is  in 
the  size,  with  less  variation  in  sculpture  and  vestiture  than  in  species 
Eos.  14,  15,  and  17. 

Distinctive  characters. — The  characters  which  serve  to  distinguish 
this  species  from  D.  rufipennis]  to  which  it  is  more  closely  allied,  are 
ii-  -lightly  smaller  size  and  more  distinctly  impressed  elytral  striae 


FIG.  8G.— Dendroctonus  murrayanse:  Distribution  map.    (Original.) 

on  the  dorsal  and  lateral  areas  and  the  finely,  densely  punctured 
interspaces  of  the  declivity  in  the  male. 

It  appears  that  this  species  has  not  been  referred  to  in  literature. 

The  pupa  has  not  been  observed. 

Larva  (PL  VIII,  fig.  19).— In  addition  to  the  generic,  divisional, 
and  subdivisional  characters,  the  front  has  an  impression  toward  the 
anterior  angles  and  a  faint  transverse  elevation  in  front  of  the  middle. 
The  clypeus  is  longer  than  the  labrum  and  marked  with  a  median 
groove,  and  with  the  apex  broadly  emarginate;  labrum  with  apex 
faintly  emarginate,  and  the  mandibles  with  distinct  dorsal  impres- 
sion. "  Larval  type  labeled  "Hopk.  I'.  S.  No.  2690c." 

Galleries. — Only  fragmentary  specimens  of  the  galleries  have  been 
observed,  but  they  appear  to  come  between  piceaperda  and  valens, 
the  larvse,  for  the  most  part,  excavating  a  common  chamber. 


142 


THE   SCOLYTID   BEETLES. 


Distribution  (fig.  86). — (Hopk.  U.  S.)  Wyoming:  Homestake,  Sar- 
atoga, Keystone,  Cheyenne  National  Forest,  and  Big  Horn  National 
Forest.  Colorado:  Jefferson.  Additional  localities  from  other  col- 
lections: (U.S.N.M.)  (H.  &  S.),  National  Park,  Wyoming. 

Host  trees. — Pinus  murrayana  and  Picea  engelmanni. 

Identified  specimens. — H.  &  S.,  5;  Hopk.  U.  S.,  over  100  specimens, 
including  adults,  larvae,  and  work. 

BIBLIOGRAPHY. 
Dendroctonus  shoshone  Hopkins,  1902a,  p.  3,  manuscript  name  only. 

20.     Dendroctonus  punctatus  Le  Conte. 

(PI.  VI,  fig.  20.) 

Adult. — Typical  female:  Length  6.5  mm.,  dark  reddish  brown. 
Head  convex,  with  moderately  distinct  anterior  impression.  Elytral 
declivity  with  striae  distinctly  impressed.  Punctures  of  pronotum 
distinct,  coarse,  irregular;  posterior  half  of  proepisternal  area  punc- 
tured; striae  of  elytral  declivity  with  coarse  punctures;  elytral  striae 
distinctly  impressed;  punctures  coarse  and  distinct;  interspaces 
rather  narrow,  convex,  moderately  rugose  on  dorsal  area,  but  nearly 
smooth  on  lateral  area.  Secondary  sexual  characters:  Declivity 
convex,  shining;  striae  distinctly  but  not  deeply  impressed;  punc- 
tures coarse  and  distinct;  interspaces  narrow,  convex,  with  row  of  I 
granules. 

Typical  female  labeled  "type  of  drawing,"  name  label,  "Hopk. 
4/25/02,  Picea  rubens,  Randolph  County,  W.  Va.,  A.  D.  Hopkins, 
collector,  9  ,  Hopk.  W.  Va.  6312." 

Variations. — There  appears  to  be  very  little  variation  in  the  few  I 
specimens  observed. 

Distinctive  characters. — This  species  is  at  once  distinguished  from  | 
all  of  the  preceding  by  the  coarse  punctures  of  the  elytral  striae, 
especially  on  the  declivity.     Its  nearest  ally  is  D.  micans,  of  Europe,  i| 
from  which  it  differs  in  its  smaller  size,  more  elongate  form,  and 
more  distinctly  impressed  elytral  striae. 

Revisional  notes. — While  the  original  description  does  not  include 
the  more  distinctive  characters,  it  was  based  on  a  type  which  was 
readily  recognized  as  a  distinct  species.  Dietz  referred  the  specimen 
in  the  Horn  collection,  labeled  D.  punctatus  Lee.,  to  D.  rufipennis 
(Kirby),  but  it  is  certainly  distinct  from  what  is  now  recognized  as  | 
D.  rufipennis. 

Host  tree. — Picea  rubens. 

Pupae,  larvae,  and  galleries  of  this  species  have  not  been  observed. 

Distribution  (fig.  87). — (Hopk.,  W.  Va.)  1  specimen  collected  by 
the  writer  May  21,  1892,  in  the  high  mountains  of  Randolph  County, 


THE   GEXUS   DENDROCTONUS. 


143 


•flTest  Virginia,  under  bark  on  spruce  stump.  (Le  Conte,  M.  C.  Z.) 
I;  specimens  labeled  "  Xe\v  York";  (Horn,  A.  E.  S.)  1  specimen 
labeled  "Pa.77 

BIBLIOGRAPHY  A  .:>  SYNONYMY. 

^enfiroctonus   punctatut  Le  Conte,   1868,    i>.    17:},    original   description,    synonymy, 

locality.     Le  Conte,  1876,  p.  385,  revision,  synonymy,  bibliography,  localities. 

Packard,  1887,  p.  177,  Le  Conte  quoted.     Packard,  1890,  p.  722,  Le  Conte  quoted. 

Hopkins,  1899a,  p.  447,  habit,  etc.,  West  Virginia.     Hopkins,  1902a,  p.  3,  recog- 

nized'as  a  good  species  and  restored. 
Dendroctonus  rufipennis  (not  of  Kirby)  Dietz,  1890,  p.  30,  Pennsylvania. 


FIG.  $7.—Dendroctonuspunctatus:  Distribution  map.    (Original.) 
21.     Dendroctonus  micans  (Kugelann). 

(PL  VI,  fig.  21.) 

Adult. — Typical  female:  Length  7.25  mm.,  dark  reddish  brown. 
I-  Head  convex,  with  faint  anterior  impression,  without  anterior  line; 
elytral  declivity  with  striae  not  deeply  impressed;  punctures  of 
pronotum  distinct,  coarse,  irregular;  posterior  half  of  proepisternal 
area  punctured;  striae  of  elytral  declivity  with  coarse  punctures; 
elytral  striae  not  impressed,  punctures  moderately  coarse,  interspaces 
broad  and  flat,  sparsely  and  finely  rugose.  Secondary  sexual  charac- 
ters: Elytral  declivity  convex,  subopaque;  striae  faintly  impressed; 
punctures  coarse  and  distinct;  interspaces  moderately  convex,  with 
sparse,  irregular  granules. 

Typical  female  labeled  "type  of  drawing,"  name  label,  "Hopk. 
4/25/02,   9  .     Determination  No.  20,  Eichhoff,  Sachsen,  Horning.77 


144  THE  SCOLYTID  BEETLES. 

Typical  male:  Length  6  mm.,  black.  Agrees  with  female  in  every 
respect,  except  that  it  may  have  stouter  mandible,  the  club  of  antenna 
smaller,  more  elongate;  the  declivity  of  elytra  with  strial  punctures 
finer,  and  the  interspaces  without  granules. 

Typical  male  labeled  ll  $ ,  from  Dr.  Severin." 

Variations. — Length  7  to  8  mm.,  average  about  7.5  mm.;  uniform 
reddish  brown  to  nearly  black,  with  usual  variation  in  sculpture  and 
vestiture. 

Distinctive  characters. — This  species  is  more  closely  allied  to  D. 
punctatus  than  to  any  of  the  other  species  of  the  genus,  from  which 
it  is  distinguished  by  its  larger  size  and  stouter  form,  with  the  striae 
scarcely  at  all  impressed,  and  the  punctures  smaller. 

The  male  of  this  species  appears  to  be  far  more  rare  than  in  the 
other  species,  from  the  fact  that  among  83  specimens  examined  only 
2  males  were  found.  While  the  declivity  is  somewhat  more  shining 
and  smoother  in  the  male,  this  character  is  by  no  means  as  striking 
as  in  the  other  species  of  the  section  to  which  it  belongs. 

The  pupa  has  not  been  studied  by  the  writer,  but  is  evidently 
similar  in  general  character  to  that  of  D.  piceaperda. 

Larva. — Abdominal  tergite  8  without,  9  with,  small  dorsal  plate, 
which  is  not  rugose.  Front  with  distinct  elevation.  In  addition  to 
the  generic,  divisional,  and  subdivisional  characters,  the  frontal 
elevation  is  subopaque,  transversely  wrinkled,  situated  in  front  of 
the  middle  and  joined  to  the  epistoma;  lateral  angles  are  curved 
back  to  their  junction  with  the  frontal  sutures,  which  are  broadly 
curved  toward  the  apex.  The  area  behind  the  elevation  is  broad,  \ 
flat,  and  more  shining.  Clypeus  broad,  with  faint  median  groove 
and  the  apex  broadly  emarginate.  Labrum  small,  rather  stout,  with 
broad  dorsal  impression,  the  apex  subtruncate;  mandibles  shining, 
with  a  distinct  dorsal  impression  and  oblique  ridge  near  the  middle; 
sternellar  lobes  of  the  thoracic  segments  moderately  prominent  and 
with  distinct  foot  calli. 

Type. — One  of  a  large  series  of  larvae  received  from  Dr.  G.  Severin, 
conservateur,  Royal  Museum  of  Natural  History,  Belgium. 

The  larva  of  this  species  is  at  once  distinguished  from  that  of  all 
of  the  other  species  of  the  genus,  so  far  as  observed,  by  the  faint 
dorsal  plate  of  the  ninth  abdominal  segment,  by  the  absence  of  a 
plate  on  the  eighth,  by  the  frontal  elevation  connected  with  the 
epistoma,  and  by  the  greater  number  and  more  distinct  hairs  on  the 
scutellar  lobes  of  the  thorax  and  abdomen. 

Galleries  (fig.  88). — The  galleries  are  evidently  quite  similar  to 
those  of  D.  terebrans  and  D.  valens,  especially  in  the  fact  that  the 
larvae  live  together  in  a  common  chamber  exposed  in  the  inner  bark. 
According  to  Dr.  G.  Severin,  the  egg  gallery  is  vertical,  frequently 


THE   GENUS  DENDROCTONUS. 


145 


and  somewhat  irregular,  sometimes  doubly  inflected  and 
>in  12  to  20  cm.  long.  The  female  here  deposits  from  20  to  25 
in  several  places.  The  larvae  eat  very  close  together,  growing 
equally  in  size  and  age  and  making  a  common  cavity  underneath 
the  bark.  In  order  to  go  through  the  pupal  stage,  they  return  to 
the  large  space  which  they  left  behind  them  and  which  is  now  filled 
with  excrement  and  resin.  Departing  from  their  common  cavity, 
they  eat  out  isolated  galleries,  and  at  the  end  of  these  they  pupate. 


FIG.  S8.—Dendroctonus  micans:  Egg  galleries  and  larval  chamber.  A ,  Basal  sections  of  egg  galleries;  B, 
advanced  stage  of  work;  a,  entrance  burrow;  6,  excavated  July  8-16;  c,  excavated  July  8-29;  d,  eight 
days  old;  e,  three  weeks  old;  /,  basal  section;  g,  boring-dust;  h,  subsequent  or  inner  gallery  ("mother 
gallery");  j,egg  nest  with  eggs  scattered  about  in  boring-dust;  k,  social  chamber  excavated  by  larvae; 
I',  boring-dust  and  resin;  m,  larvae  at  work.  (Adapted  from  Pauly  Forstlich-natur  wissenschaftliche 
Zeitschrift,  I  Jahrgang,  figs.  3  and  4.) 

Distribution  (fig.  89). — According  to  the  literature,  this  species 
ranges  from  central  to  northern  Europe  and  from  Denmark  and 
Russia  eastward  into  Siberia. 

Host  trees. — It  is  said  to  infest  Pinus,  Picea,  Abies,  and  Larix. 

Identified  specimens. — The  wTiter  has  examined  1  specimen  received 
from  W.  EichhofF,  8  from  B.  W.  Schlick,  Denmark;  2  with  specimens 
of  work  from  Reitter's  collection,  collected  in  Bohemia,  and  about  70 
specimens  of  adults,  as  well  as  larvae  and  specimens  of  work  from 
Dr.  G.  Severin,  of  the  Muse"e  Royale  d'Histoire  Naturelle,  Brussels> 
Belgium. 

79980—09 11 


146 


THE   SCOLYTID   BEETLES. 


BIBLIOGRAPHY  AND  SYNONYMY. 


?Bostrichus  ligniperda  Herbst,  1793,  p.  107  (in  part). 

Bostrichus  micans  Ktigelann,  1794,  p.  523,  original  description. 

?  Hylesinus  ligniperda  Gyllenhal,  1813,  pp.  335,  336  (in  part). 

Dendroctonus  micans  (Kug.)  Erichson,  1836,  p.  53,  type  of  genus.  Bach,  1849,  p.  144. 
Stein,  1854,  pp.  277-279,  habits,  destructiveness.  Kollar,  1858,  pp.  23-28,  habits, 
control.  Eichhoff,  1864,  p.  27,  pi.  1,  fig.  5,  tarsi,  fig.  6,  maxilla,  fig.  7,  labium,in 
revision  of  genus.  Lacordaire,  1866,  p.  360,  in  revision  of  genus.  Chapuis,  1869, 
p.  35;  1873,  p.  243,  revised  description.  Lindemann,  1875,  pp.  213,  221,  pi.  1,  figs. 
1-10,  male  reproductive  organs  described  and  illustrated.  Eichhoff,  1881, 
pp.  125-128,  fig.  23,  adult,  fig.  24,  galleries,  revision,  bibliography,  account 
of  habits,  distribution,  etc.  Altum,  1881,  pp.  262-266,  description,  biology. 
Judeich  and  Nitsche,  1889,  pp.  458-462,  life  history,  habits,  importance,  remedy. 
Pauly,  1892,  pp.  315-327,  4  figs,  of  galleries,  habits.  Verhoeff,  1896,  pp.  124-133, 
anatomy.  Mene"gaux  &  Cochon,  1897,  pt.  2,  p.  120,  habits,  etc.  Severin,  1902, 
p.  145,  habits  in  Belgium.  Weber,  1902,  p.  108,  fig.  5,  enemy.  Brichet  et 
Severin,  1903,  pp.  244-258,  habits,  etc.  Baudisch,  1903,  pp.  151-152,  habits,  etc. 
Quairi^re,  1904,  pp.  626-628.  Nusslin,  1905,  pp.  175-178,  habits,  description, 
importance.  Quievy,  1905,  pp.  334,  335.  Severin,  1908,  pp.  1-20,  description, 
habits,  depredations,  control. 

Hylesinus  micans  (Kug.)  Ratzeburg,  1839,  p.  217,  Taf.  VII,  fig.  3,  adult. 

Hylesinus  (Dendroctonus)  micans  (Kug.)  Ratzeburg,  1839,  p.  217,  Taf.  VII,  fig.  3, 
adult;  Taf.  VIII,  figs.  1,  2,  3,  galleries,  young  larvae,  pupae. 


FIG.  89.— Dendroctonus  micans:  Distribution  map.    (Original.) 
SUBDIVISION  D. 

The  distinguishing  characters  common  to  the  species  of  the  fourth 
subdivision  are: 

Adult. — Front  without  median  or  posterior  impression.  Prono- 
tum  somewhat  elongate,  slightly  narrower  than  elytra,  moderately 
constricted  toward  head,  with  regular  punctures  or  without  coarse 
and  fine  punctures  intermixed,  long  hairs  absent  on  median  and 
posterior  dorsal  areas,  present  on  anterior  and  lateral  areas;  head 


THE   GENUS   DENDROCTONUS.  147 

,  broad,  convex;  epistomal  process  and  elytral  rugosities  variable 
within  the  same  species. 

Sexes. — Females  with  front  of  head  moderately  broad;  mandibles 
'shining,  moderately  stout;  antenna!  club  broad  and  stout;  elytral 
declivity  slightly  more  rugose ;  striae  impressed  with  distinct  punc- 
tures. 

Males  with  front  of  head  distinctly  broader;  mandibles  opaque, 
stout;  antennal  club  narrow,  more  elongate,  and  the  elytral  declivity 
slightly  less  rugose;  striae  less  distinctly  impressed,  and  the  punctures 
more  obscure. 

Pupa. — Vertex  of  head  convex;  front  and  middle  femur  each  with 
a  minute  subapical  spine;  abdominal  tergites  with  moderately  dis- 
tinct spines. 

Larva. — Abdominal  tergites  8  and  9  with  distinct  dorsal  plates, 
each  armed  with  three  prominent  teeth. 

Galleries. — Egg  galleries  slightly  winding  to  nearly  straight;  larval 
mines  not  separated,  except  very  rarely  near  the  outer  extremity, 
but  forming  broad  common  larval  chambers. 

22.     Dendroctonus  terebrans  (Olivier). 

(PI.  VII,  fig.  22.) 

Adult. — Typical  female:  Length  5.6  mm.,  black.  Front  convex, 
without  impressions;  epistomal  process  moderately  broad,  lateral 
angles  tuberculate.  Pronotal  punctures  very  coarse,  regular,  mod- 
erately dense,  scarcely  decreasing  in  size  toward  base;  elytra  with- 
out long  hairs  toward  base. 

Typical  female  labeled,  name  label,  "Hopk.  1/22/08,  Pinus  echi- 
nata,  Hopkins,  collector,  Tryon,  N.C.,  9  ,  Hopk.  U.  S.  530aa." 

Typical  male:  Length  5.6  mm.  Differs  from  female  in  stouter 
mandibles  and  slightly  coarser  rugosities  of  elytral  declivity. 

Typical  male  labeled  same  as  female. 

Variations. — The  length  varies  from  5  to  8  mm.,  with  the  average 
about  7  mm.  The  color  ranges  from  piceous  to  deep  black,  the  latter 
prevailing.  Immature  specimens  are  reddish,  but  fully  matured 
ones  are  always  darker  than  the  darkest  D.  valens.  The  greatest 
variation  is  in  size,  and  while  the  usual  variation  prevails  in  some  of 
the  other  characters,  it  is  much  less  so  than  in  D.  valens.  In  New 
Jersey,  Pennsylvania,  Virginia,  and  West  Virginia,  where  there  is  an 
overlapping  of  the  range  of  D.  valens  and  D.  terebrans,  specimens  are 
sometimes  found  which  appear  to  be  hybrids,  but  it  appears  that  the 
more  dominant  characters  of  D.  terebrans  prevail  in  such  hybrids,  so 
that  the  darker  color  and  coarse  punctures  of  the  pronotum  serve  to 
distinguish  them  as  being  more  closely  allied  to  the  latter  species. 

Distinctive  characters. — The  characters  which  serve  to  distinguish 
this  species  from  D.  valens,  to  which  it  is  more  closely  allied,  are  its 


148  THE  SCOLYTID  BEETLES. 

prevailing  black  or  dark  color,  the  more  uniform  and  coarser  punctures 
of  the  pronotum,  the  narrower  epistomal  process,  with  the  angles  more 
tuberculate,  and  the  less  evident  long  hairs  on  the  anterior  dorsal 
area  of  the  elytra. 

Revisional  notes. — While  the  type  of  this  species  has  not  been  seen 
by  the  writer,  it  is  clearly  evident  from  Olivier's  description  and 
figures  (Olivier,  1795)  that  the  large  black  form  common  to  the 
southern  United  States  represents  the  species  described.  The  only 
distinctive  specific  character  mentioned,  however,  is  the  reference  to 
the  Black  Scolytus  and  to  the  body  being  black,  brown,  or  brownish- 
black.  The  confounding  of  Dendroctonus  valens  and  D.  terebrans  under 
the  latter  name  has  resulted  in  much  confusion  in  the  literature.  With 
our  present  knowledge,  however,  it  is  not  difficult  to  clear  up  some 
of  the  confusion  and  to  revise  and  correct  the  literature  so  that  it 
may  be  known  in  many  cases  whether  or  not  one  or  both  species  was 
included  in  a  given  reference.  Erichson,  1836,  Lacordaire,  1866,  and 
Chapuis,  1869,  evidently  did  not  compare  D.  valens  and  D.  terebrans. 
While  a  specimen  of  this  species  has  been  in  the  Harris  collection  since 
1839,  Harris  apparently  made  no  reference  to  its  characters.  Zimmer- 
man, 1868,  page  149,  did  not  mention  D.  valens,  but  evidently  had  the 
two  species  confused  in  his  revised  description.  Le  Conte,  1868,  page 
173,  referred  D.  valens  to  D.  terebrans,  and  in  1876,  pages  384-385, 
confuses  the  characters  and  distribution  of  the  two  species.  Dietz, 
1890,  page  29,  included  this  species  under  his  variety  a,  and  (p.  30) 
evidently  includes  two  specimens  from  Florida  under  his  revision  of 
D.  rufipennis.  In  subsequent  literature  up  to  1906  there  is  more  or 
less  confusion  of  this  species  with  D.  valens.  The  writer,  1906c,  page 
81,  restored  D.  valens  Lee.  and  called  attention  to  the  characters  dis- 
tinguishing D.  terebrans  (Oliv.) .  In  1900  the  writer  found  one  specimen 
in  the  Harris  collection,  under  Hylurgus  terebrans,  under  his  No.  99, 
referred  to  in  his  note  as  "Dark  specimen  abundant  under  bark  of 
pitch  pine,  October  27,  1839,"  but  it  appears  that  no  reference  was 
made  to  this  dark  specimen  in  any  of  his  publications.  The  locality 
is  not  given,  but  it  is  presumably. Cambridge.  It  appears  that  this 
species  was  not  represented  in  the  Horn  collection  under  D.  terebrans 
when  Doctor  Dietz  prepared  his  revision,  and  that  the  only  example 
involved  in  the  revision  under  D.  terebrans  was  the  one  in  the  Ulke 
collection  from  Pennsylvania,  designated  as  "  variety  a."  Two  exam- 
ples were  found  in  the  Horn  collection  under  D.  rufipennis,  labeled 
"Fla.,"  and  it  was  evidently  on  these  that  Doctor  Dietz  based  his 
Florida  locality  in  his  revision  of  D.  rufipennis.  In  1907  this  species 
was  represented  in  the  Le  Conte  collection  by  9  specimens  and  8  addi- 
tional specimens  in  the  general  collection  of  the  Museum  of  Com- 
parative Zoology. 


THE   GEXUS   DENDROCTONUS.  149 

Pupa. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  front  and  middle  femora  are  armed  each  with  a  minute 
apical  spine;  abdominal  tergites  1  to  6  have  moderately  small  pleura! 
spines,  1  is  without  dorsal  spine,  but  with  distinct  lateral  ones;  2  to  6 
have  small  dorsal  and  lateral  spines,  the  former  increasing  in  size  to  6. 
All  have  pale  tips;  7  and  8  unarmed;  9  with  usual  stout  pleural  spine. 
Pupal  type  labeled  "Hopk.  W.  Va.  7701." 

The  usual  variation  prevails  in  the  number  and  arrangement  of 
minor  spines  and  between  the  young  and  older  examples. 

The  character  \vhich  in  general  serves  to  distinguish  the  pupa  of 
this  species  from  the  preceding  is  found  in  the  paler  tips  of  the  body 
spines. 

Larva. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  front  of  head  with  posterior  angle  and  median  area  not 
elevated  but  transversely  rugose  except  near  apex,  where  it  is  smooth; 
epistoma  flat,  opaque,  smooth,  with  straight  anterior  margin;  clypeus 
broad,  prominent,  convex,  with  faint  median  longitudinal  line,  sides 
rounded,  apex  broadly  emarginate;  labrum  short,  with  sides  nearly 
parallel  and  apex  tuberculate.  Pro  thoracic  tergum  with  two  broad, 
shining  dorsal  plates  separated  by  a  rather  broad  median  space,  and 
a  smaller  lateral  plate  each  side;  sternellar  lobes  each  with  a  faint  foot 
callus;  mesoterga  and  metaterga  with  shining  plates  on  the  lateral 
lobes.  Abdominal  scutellar  lobes  with  a  rather  prominent  tubercle 
on  each  epipleurum.  Larval  type  labeled  "Hopk.  U.  S.  1201." 

The  larva  of  this  species  is  scarcely  to  be  distinguished  from  that  of 
D.  valens. 

Galleries. — The  egg  galleries  are  generally  longitudinal,  more  or  less 
winding,  and  vary  greatly  in  length,  sometimes  being  very  long. 
They  are  irregular  in  width,  sometimes  with  branches,  and  are  slightly 
grooved  in  the  surface  of  the  wood.  The  eggs  are  placed  in  masses  at 
intervals  along  the  sides  and  in  the  inner  bark;  the  larvae  excavate 
broad  chambers  which  vary  in  size  from  a  square  inch  to  many  square 
feet.  The  galleries  of  this  species  do  not  differ  materially  from  the 
following,  and  have  a  wide  range  of  variation  in  size  and  general 
character. 

Distribution  (fig.  90). — (Hopk.  U.  S.)  Alabama:  Calhoun.  Dela- 
ware. District  of  Columbia:  Takoma.  Georgia:  Cornelia,  Thomas- 
ville.  New  Jersey:  Lakewood,  New  Brunswick.  New  York:  Islip 
(Long  Island).  South  Carolina:  Chicora,  Lumber,  New  Landing, 
Pregnall.  Texas:  Austin,  Call,  Deweyville,  Kirbyville,  Tarkington. 
Virginia:  Glen.  West  Virginia:  Kanawha  Station.  (Hopk.  W.  Va.) 
West  Virginia:  Crow,  Marion  County,  Morgantown,  Romney.  Addi- 
tional localities  from  other  collections:  (Le  Conte)  Georgia,  North 
Carolina,  New  Hampshire,  Pennsylvania.  (M.  C.  Z.)  Texas,  South 


150 


THE    SCOLYTID   BEETLES. 


Carolina,  Maryland.  (A.  E.  S.)  New  Jersey,  Delaware.  (A.  N.  S.) 
Marion  County,  Fla.  (U.S.N.M.)  Lakewood,  N.  J.  (D.  A.)  Islip, 
Long  Island,  N.  Y.  (Laurent)  Pennsylvania. 

Host  trees. — Pinus  palustris,  P.  rigida,  P.  tseda,  P.  serotina,  P. 
strobus,  P.  echinata,  Picea  rubens. 

Identified  specimens. — Le  Conte,  9  specimens;  M.  C.  Z.,  8;  Horn,  7; 
U.S.N.M.,  2;  H.  &  S.,4;  D.A.,7;  Hopk.  U.  S.,  about  400  specimens, 
including  adults,  larvae,  and  work. 


FIG.  90.— Dendroctonus  terebrans:  Distribution  map.    (Original.) 

BIBLIOGRAPHY  AND  SYNONYMY. 

Scolytus  terebrans  Olivier,  1795,  p.  6,  PL  I,  fig.  6,  adult;  original  description,  locality 
southern  U.  S.  (Southern  Georgia,  Schwarz). 

Dendroctonus  terebrans  (Oliv.)  Eri'chson,  1836,  p.  53  (cotype  of  genus).     Lacordaire,  j 
1866,  p.  360.     Zimmerman,  1868,  p.  149  (in  part),  South  Atlantic  States.     Le 
Conte,  1868,  p.  173  (in  ]4rt).     Chapuis,  1869,  pp.  35-36.     Chapuis,  1873,  pp. 
243-244,  revision,  Texas.     Schwarz,  1878,  p.  469,  list,  Florida.     Packard,  1887,, 
p.  177  (in  part),  Le  Conte  quoted.     Packard,  1890,  p.  721  (in  part).     Dietz, 
1890,  p.  29  (in  part).     Hopkins,  1893b,  p.  143,  No.  76  (in  part),  Hampshire  andi 
Monongalia  counties,  W.  Va.     Hopkins,  1893c,  p.  213,  No.  300  (in  part),  list, 
host,   etc.     Smith,    1899,   p.   364   (in  part),    distribution,   habits.     Chittenden, 
1899,  p.  56  (in  part).     Smith,  1901,  p.  92,  destructive  to  pine,  Lahaway  [Borden- 
town],  N.  J.     Ulke,  1902,  pp.  36-56,  list,  habits,  etc.     Hopkins,  1902b,  p.  10, 
footnote,    mention.     Hopkins,    1906c,    p.   81,    distinguishing  characters.     Felt, 
1906,  pp.  342-345,  Long  Island. 

Dendroctonus  terebrans  (Lacordaire)  Le  Conte,  1876,  p.  385  (=  Oliv.  in  part),  bibli- 
ography, distribution,  systematic  note,  on  specimens  from  Georgia. 

Dendroctonus  rufipennis  (not  of  Kirby)  Dietz,  1890,  p.  30,  Florida. 

fDendroctonus  sp.  Blandford,  1897,  p.  147,  reference  to  black  form  from  Texas. 


THE   GENUS   DENDROCTONUS.  151 

23.     Dendroctonus  valens  Le  Conte. 
(PL  VII,  fig.  23.) 

Adult. — Typical  female:  Length,  8.7  mm.  Head  with  front  broad, 
convex,  and  with  broad  anterior  impression.  Epistomal  process 
broad,  with  lateral  sections  oblique.  Pronotum  with  punctures 
moderately  coarse,  much  smaller  and  denser  toward  base.  Elytra 
with  a  few  long  hairs  toward  base;  declivity  convex;  striae  impressed, 
with  small  distinct  punctures;  interspaces  moderately  convex,  dis- 

rctly  rugose. 
Typical   specimen   labeled,   name   label,    "Hopk.    1/22/08,  Pinus 
ponderosa,  Hopkins,  collector,  McCloud,  Cal.,   9  ,  Hopk.  U.  S.  18a." 

Typical  male:  Length  7.6  mm.  Differs  from  female  in  stouter 
mandibles,  narrower  antennal  club,  more  opaque  declivity,  less  dis- 
tinctly impressed  striae,  and  more  obscure  punctures. 

Typical  male  labeled  same  as  female. 

Variations. — The  length  ranges  from  5.7  to  9  mm.,  with  the  aver- 
age about  8  mm.  The  color  of  the  elytra,  pronotum,  and  vertex 
of  head  ranges  from  light  to  dark  red,  but  is  never  black,  while  the 
ventral  part  of  the  body  varies  from  light  red  to  black.  The  great- 
est variation  is  in  size,  but  there  is  a  wide  and  remarkable  range 
in  the  epistoma  and  front  and  in  the  sculpture  of  the  pronotum 
and  elytra,  as  in  almost  every  other  character.  Thus  a  large  num- 
ber of  individuals  may  be  easily  selected,  each  of  which  might  be 
considered  as  representing  a  good  species,  but  when  a  large  series 
of  specimens  is  examined  from  any  given  faunal  region  or  locality 
no  sufficiently  distinctive  and  constant  characters  have  been  found 
by  which  they  can  be  readily  recognized  as  distinct  from  those  of 
any  other  faunal  region,  so  that  those  examples  from  Maine  can 
not  be  distinguished  from  examples  collected  in  the  mountains  of 
Mexico. 

Distinctive  characters. — The  characters  which  serve  to  distinguish 
this  species  from  D.  terebrans,  to  which  it  is  closely  allied,  are  its 
prevailing  red  color,  the  less  uniform  and  more  densely  placed 
pronotal  punctures,  the  much  broader  epistomal  process,  with  the 
lateral  sections  less  angular  and  more  oblique,  and  the  more  evident 
and  numerous  hairs  on  the  anterior  dorsal  area  of  the  elytra. 

Revisional  notes. — See  same  heading  under  D.  terebrans. 

The  typical  specimen  on  which  Le  Conte's  original  description 
(Le  Conte,  1860)  was  based  is  from  California  and  represents  the 
common  red  form  which  has  heretofore  been  confused  with  D.  tere- 
brans. The  distinguishing  character,  "  finer  and  denser  punctures  of 
the  thorax,"  mentioned  by  Le  Conte  is  undoubtedly  a  good  specific 
character  when  taken  with  color  and  other  characters.  The  species 
is  represented  in  the  Le  Conte  collection  by  the  type  and  9  speci- 


152 


THE    SCOLYTID   BEETLES. 


mens,  and  in  the  collection  of  the  Museum  of  Comparative  Zoology 
by  over  50  specimens. 

Pupa. — In  addition  to  the  generic,  divisional,  and  subdivisional 
characters,  the  front  and  middle  femora  are  armed  each  with  a 
minute  apical  spine;  abdominal  tergites  1  to  6  with  moderately 
small  pleural  spines;  1  is  without  dorsal  spines,  but  with  distinct 
lateral  ones;  2  to  6  have  small  dorsal  and  lateral  spines,  the  former 
increasing  in  size  to  6,  and  all  have  dark  tips;  7  and  8  are  unarmed; 
9  has  the  usual  stout  pleural  spine.  Pupal  type  labeled  "Hopk. 
U.S.  2824."- 


FIG.  9l.—Dendroctonus  valens:  Egg  galleries  and  larval  chamber.  A ,  Incomplete  egg  galleries  with  boring 
dust  removed;  B,  normal  gallery;  C,  advanced  stage  of  work;  a,  entrance  burrow;  b,  basal  section; 
c,  ventilating  burrow^  d,  egg  nest  with  eggs;  e,  boring  dust;  /,  subsequent  or  inner  galleries;  g,  larvae 
at  work;  h,  pupal  cell  in  boring  dust  mixed  with  resin.  (Original.) 

The  usual  variation  prevails  in  the  number  and  arrangement  of 
minor  spines  and  between  the  young  and  older  examples. 

The  character  which  in  general  serves  to  distinguish  the  pupa  of 
this  species  from  the  preceding  is  found  in  the  darker  tips  to  the 
body  spines. 

Larva  (text  fig.  39  and  PL  VIII,  fig.  23). — In  addition  to  the  ge- 
neric, divisional,  and  subdivisional  characters,  front  of  head  with  pos- 
terior angle,  median  area  not  elevated  but  transversely  rugose,  except 
near  apex,  where  it  is  smooth;  epistoma  flat,  opaque,  smooth,  with 
straight  anterior  margin ;  clypeus  broad,  prominent,  convex,  with  faint 
median  longitudinal  line,  sides  rounded,  apex  broadly  emarginate; 


THE   GENUS  DENDROCTONUS. 


153 


labrum  short,  sides  nearly  parallel,  and  apex  tuberculate.  Protho- 
raric  tergum  with  two  broad,  shining  dorsal  plates  separated  by  a 
rather  broad  median  space,  and  a  smaller  lateral  plate  each  side; 
stfrnellar  lobes  each  with  a  faint  foot  callus;  the  mesoterga  and 
nu'taterga  with  shining  plates  on  the  lateral  lobes.  Abdomen  with  a 
rather  prominent.tubercle  on  each  epipleurum.  Larval  type  labeled 
"Hopk.  U.  S.  2824." 


FIG.  \+2.—Dcndroctonw  valens:  Work  in  bark  at  base  of  stump,  a,  Entrance  and  pitch  tube;  b,  egg  gallery; 
c,  boring  dust  and  resin;  d,  pupal  cell;  e,  pupa;  /,  larvae  at  work  feeding  on  inner  living  bark;  g,  exit 
burrows;  h,  resulting  old  scar  or  basal  wound,  often  referred  to  as  basal  fire  wound;  i,  inner  bark  with 
outer  corky  bark  removed.  (  Original. ) 

The  larva  of  this  species  is  scarcely  to  be  distinguished  from  the 
preceding. 

Galleries  (figs.  91-93). — The  egg  galleries  are  generally  longitudinal, 
more  or  less  winding,  and  vary  greatly  in  length,  sometimes  being 
very  long;  they  are  irregular  in  width  and  sometimes  with  branches, 
and  are  slightly  grooved  into  the  surface  of  the  wood.  The  eggs 
are  placed  in  masses  at  intervals  along  the  sides  in  the  inner  bark, 
and  the  larvae  excavate  broad  chambers,  which  vary  in  size  from  a 


154 


THE    SCOLYTID   BEETLES. 


square  inch  to  many  square  feet.  The  galleries  of  this  species  do  ; 
not  differ  materially  from  the  preceding,  and  have  a  wide  range  of  j 
variation  in  size  and  general  character. 

Distribution  (fig.  94). — (Hopk.  U.  S.)  Arizona:  Chiricahua  Moun-  j 
tains,  Flagstaff,  Fredonia,  Grand  Canyon,  Paradise,  Kamsey  Canyon,  | 
Rincon  Mountains,  Santa  Catalina  National  Forest,  Williams.     Calif  or-  \ 
nia:  Alder  Creek,  Berkeley,  Chester,  Del  Monte,  La  Moine,  Little  Yosem- 
ite,  Madera  County,  Merced,  McCloud,  Nevada  City,  Pacific  Grove, 
Palo    Alto,    Pinogrande,    San    Bernardino,    Sterling,    Summerdale, 
Wawona,    Yosemite.     Canada.     Colorado:  Fort    Garland,    Manitou  j 
Park,  Palmer  Lake,  San  Isabel  National  Forest.     Guatemala:  C^bon.  j 


FIG.  Q3.—Dendroctonus  valens:  Basal  wound  in  living  tree  resulting  from  primary  injury  by  this  species. 
Often  mistaken  for  fire  wound.    (Original.) 

Idaho:  Cedar  Mountain,  Centerville,  Grimes  Pass,  Harris  Ridge 
(Kooskai),  Pioneerville,  Priest  River,  Smiths  Ferry.  Kansas. 
Maine:  Brunswick,  Casco  Bay,  Limerick,  Peak  Island,  Portland. 
Massachusetts:  Lynn,  Wyoming.  Mexico:  Chalco,  Chihuahua,  Mex- 
ico City,  Michoacan,  Ponada,  Satazin.  Michigan:  Grand  Island. 
Montana:  Missoula.  Nevada.  New  Hampshire:  Durham,  Webster. 
New  Mexico:  Capitan,  Capitan  Mountains,  Cloudcroft,  Lincoln 
National  Forest,  Vermejo,  White  Mountains.  New  York:  Ithaca. 
North  Carolina:  Biltmore,  Pink  Beds.  Oregon:  Albany,  Hood  River, 
Joseph,  Slate  Creek.  Pennsylvania:  Milford,  Philadelphia.  South 


THE   GENUS  DENDROCTONUS. 


155 


Dakota:  Black    Hills,    Elmore,    Lead,    Spearfish.      Utah:  Escalante, 

Kajnas,     Kanab,     Panguitch     Lake.      Vermont:  Fairlee.      Virginia. 

Washington:  Buckeye,    Easton,    Pullman,    Skykomish.      West     Vir- 

(fin'ni:  Crow,  Hampshire  County,  Hardy  County,  Kanawha  Station, 


FIG.  94.—Dendroctonus  valens:  Distribution  map.    (Original.) 

Monongalia  County,  Morgantown,  Pendleton,  Raleigh  County, 
Romney,  Roosevelt,  Tucker.  Wisconsin:  Ashland,  Madison.  (Hopk. 
W.  Va.)  West  Virginia:  Bretz,  Cranesville,  Deckers  Creek,  Dellslow, 
Mayfield  Hill,  Moorefield,  Morgantown,  Pendleton,  Randolph, 


156  THE  SCOLYTID  BEETLES. 

Romney.  Additional  localities  from  other  collections:  (M.  C.  Z.)  New 
Mexico;  California;  Pennsylvania;  Idaho;  Maine;  Massachusetts; 
Cambridge,  Mass.  (Le  Conte)  Middle  States;  Connecticut;  Garland, 
Colo. ;  California.  (Horn)  North  Carolina,  Oregon,  Wisconsin,  Maine, 
California,  New  Mexico,  and  Pennsylvania.  (A.  E.  S.)  Kansas,  Idaho, 
Nevada,  Colorado,  Canada,  Virginia,  Illinois,  New  Jersey.  (W.  &  F.) 
Durham,  N.  H.  (U.S.N.M.,  H.  &  S.)  Marquette,  Mich.;  Cambridge, 
Mass.;  Helena,  Mont.;  Garland,  Colo.;  Coeur  d'Alene,  Idaho;  Hood 
Hi ver,  Oregon ;  Chiricahua  Mountains,  Arizona ;  Sisson,Cal. ;  Coldridge, 
N.  Mex.  (U.S.N.M.,  B.  &  S.)  Las  Vegas,  N.  Mex.;  Bright  Angel, 
Prescott,  Flagstaff,  and  Williams,  Ariz.  (Gillette)  Colorado;  Bailey, 
Colo.  (U.S.N.M.)  Easton,  Wash. ;  Placer,  Colo. ;  Shasta  County,  Cal. ; 
Powder  River,  Colorado;  Lake  Superior;  Skokomish  River,  Wash- 
ington; New  Mexico;  Siskiyou  County,  Cal.;  Ozumba  Mountain, 
Mexico.  (Weed  &  Fiske)  Durham,  N.  H.  (Webb)  Pullman,  Wash. 
(Dietz)  Pennsylvania,  California,  Arizona,  Washington  [State]. 
(D.  A.)  Dunsmuir,  Cal.;  Custer  County,  Cal.  (Chittenden)  Duluth, 
Minn.;  Ithaca,  N.  Y.;  Grangeville,  Idaho;  California.  (Baldwin) 
Ventura  County,  Cal.  (Soltau)  Colorado. 

Host  trees. — Pinus  ponderosa,  P.  strobus,  P.  radiata,  P.  tigida, 
P.  lambertiana,  P.  murrayana,  P.  strobiformis,  P.  chihuahuana,  P. 
edulis,  P.  jeffreyi,  P.  sylvestris,  P.  virginiana,  P.  arizonica,  P.  sp.; 
Picea  canadensis,  P.  excelsa,  P.  rubens;  Abies  concolor;  Larix  laricina. 

Identified  specimens. — Le  Conte,  10  specimens;  M.  C.  Z.,  55;  Horn, 
14;  A.  E.  S.,  8;  U.S.N.M.,  12;  H.  &  S.,  20;  Dietz,  5;  D.  A.,  3  speci- 
mens. This  species  is  also  represented  in  the  forest  insect  collection 
of  this  Bureau  by  about  5,000  specimens,  including  all  stages  and 
work. 

BIBLIOGRAPHY  AND  SYNONYMY. 

Scolytus  terebrans  (not  of  Oliv.)  Harris,  1826,  pp.  169, 170,  character  and  habits.  Har- 
ris, 1862,  p.  86,  footnote,  name  only.  Zimmerman,  1868,  p.  149,  as  synonym  for 
D.  terebrans  (in  part). 

Hylurgus  terebrans  (not  of  Oliv.)  Harris,  1841,  p.  72,  brief  description  of  larva?  and 
habits.  Harris,  1842,  pp.  72,  73,  repeated.  Harris,  1852,  p.  76,  repeated.  Fitch, 
1858,  pp.  728-729,  description  of  adult  and  larva,  habits?  Harris,  1862,  p.  86, 
repeated,  fig.  42,  adult.  Harris,  1863,  pp.  84-86,  fig.  42,  adult,  account  repeated. 
Thomas,  1876,  p.  146,  brief  description  of  adult  and  habits  of  larva.  Smith,  1877, 
p.  52,  work  in  pine. 

Dendroctonus  valens  Le  Conte,  1860,  p.  59,  original  description.  Le  Conte,  1868,  p. 
173,  mentioned  as  synonym  of  D.  terebrans  Lacordaire.  Chapuis,  1869,  p.  35; 
Chapuis,  1873,  p.  243.  Le  Conte,  1878,  p.  472,  list,  Atlanta,  Idaho.  Hopkins, 
1903a,  p. 61,  reference  to  habits,  etc.  Hopkins,  1904,  p.  19,  PI.  VII,  figs,  a,  6,  g 
(reprint).  Powell,  1904,  anatomy.  Powell,  1905,  ibid.  Hopkins,  1905,  pp.  6, 
11,  17,  distinctive  characters.  Hopkins,  1906b,  p.  147,  PI.  IV,  figs.  6,  8,  anatomy 
of  larval  head.  Hopkins,  1906c,  p.  81,  mentioned  as  a  good  species,  host, 
localities,  etc.  Fall,  1907,  p.  218,  list,  localities. 


THE   GENUS   DENDROCTONUS. 


i 


157 


D<n<froctonus  tcrebrans  (not  of  Oliv.)  Zimmerman/,  1868,  p.  149  (in  part),  revision.  Le 
Conte,  1868,  p.  173  (in  part),  synopsis,  bibliography.  Le  Baron,  1871  (in  part), 
economic  reference.  Le  Conte,  1876,  p.  385  (in  part),  revision,  synopsis,  bibli- 
ography, locality.  Packard,  1887,  pp.  175,  243  (in  part).  Packard,  1890,  p.  721, 
fig.  250  (in  part),  adult,  quotes  Harris  and  Le  Conte.  Dietz,  1890,  p.  29  (in 
part),  Eastern  States,  California,  Washington,  fig.  1,  antenna  and  epistoma;  var. 
b,  Washington,  California,  Colorado,  Arizona,  and  Idaho;  var.  c,  New  Mexico, 
Arizona,  Nevada,  California;  var.  d,  Pennsylvania.  Hopkins,  1892a,  pp.  64-65 
(in  part),  habits,  etc.  Hopkins,  1893b,  p.  143,  No.  76  (in  part),  and  index, 
habits,  distribution,  host,  enemies,  etc.,  in  West  Virginia,  all  except  part  of  two 

Preferences  from  Hampshire  and  Monongalia  counties.  Hamilton,  1895,  pp.  346, 
378,  list,  etc.  Wickham,  1896a,  p.  169,  listed,  Lake  Superior.  Wickham,  1906b, 
p.  170,  list,  Coolidge,  N.Mex.;  Walnut  and  Williams,  Ariz.  Hopkins,  1897a,  p. 
41,  habits,  etc.  Blandford,  1897,  pp.  146-147,  synopsis,  redescribed,  distribu- 
tion in  Mexico,  bibliography.  Wickham,  1898,  p.  312,  list,  Arizona.  Hopkins, 
1899a,  pp.  392-393,415-421,  and  index  (in  greater  part),  different  stages,  galleries, 
etc.,  described  and  illustrated  (except  egg  and  pupa),  with  full  account  of  habits, 
and  distribution  in  West  Virginia,  etc.  Hopkins,  1899b,  pp.  14,  15,  habits,  hosts, 
etc.  Hopkins,  1899c,  p.  343  (in  part),  stridulation,  etc.  Chittenden,  1899,  p. 
56  (in  part).  Wickham,  1902,  p.  309,  list,  locality.  Felt,  1903,  pp.  480-481, 
figs.  1-3  (in  part),  adult,  larva,  pupa,  New  York  State  except  Long  Island  (in 
part?),  habits,  hosts,  enemies,  etc.  Felt,  1906,  pp.  342-345  and  index,  fig.  64, 
adult;  65,  pupa;  66,  larva  (in  part),  habits,  host,  etc. 

Dendroctonus  terebrans  (not  of  Lacordaire)  Le  Conte,  1868,  p.  173. 

Dendroctonus  obesus  (not  of  Mann.)  Packard,  1877,  p.  803,  description  and  probable 
habits  in  Colorado,  compared  with  D.  terebrans  (not  of  Oliv.). 

?Dendroctonus  rufipennis  (not  of  Kirby)  Packard,  1887,  p.  176,  in  pitch  pine. 

fDcndroctonus  similis  (not  of  Lee.)  Slosson,  1902,  p.  319,  list,  locality. 

Dendroctonus  valens  Lee.  var.  occidentalis  Hopkins,  1902b,  p.  12,  manuscript  name  for 
variety. 

Dendroctonus  (terebrans)  var.  valens  (Lee.)  Wickham,  1902,  p.  309,  Garland,  Colo. 

24.     Dendroctonus  adjunctus  Blandford. 
ORIGINAL   DESCRIPTION. 

"Long.  4.6-5.3  millim. 

11  Oblong,  less  elongate  than  D.  parallelocollis ,  slightly  depressed, 
piceous-black,  with  apex  of  elytra  lighter.  Median  segment  of 
epistoma  shorter  than  the  lateral  segments,  its  sides  very  oblique  and 
elevated,  its  apical  border  concave :  front  covered  with  close  granules 
and  punctures,  with  an  interrupted  median  impressed  line  deepest  at 
its  junction  with  a  slight  transverse  subocular  impression;  vertex 
finely  punctured;  antennae  piceous,  the  scape  with  rounded  club, 
second  joint  of  funiculus  scarcely  longer  than  first,  club  transverse 
oval,  its  sutures  curved  toward  apex.  Pro  thorax  more  transverse 
than  in  D.  parallelocoUis ,  constricted  in  front,  the  apical  emargination 
and  basal  bisinuation  distinct;  surface  impressed  behind  apex  and 
somewhat  flattened,  shining,  the  punctures  sparse  and  not  strong,  the 
median  line  obsolete.  Elytra  feebly  striato-punctate,  shining,  except 


158 


THE    SCOLYTID   BEETLES. 


at  the  closely  granulate  base,  with  somewhat  scattered  granules, 
obsolete  on  the  declivity,  interstices  with  rows  of  distinct  long  dark 
hairs  from  middle  to  apex,  the  first  with  a  single  series  of  stronger 
granules.  Legs  piceous. 


FIG.  95.—Dendroctonus  adjunctus:  Distribution  map.    (Original.) 

' 'Hob.  [See  fig.  95.]     Guatemala,  Totonicapam  (Champion). 
i(A  distinct  species,  resembling  a  Myelophilus  rather  than  a  Den- 
droctonus.     But  two  specimens  were  taken." 

BIBLIOGRAPHY. 
Dendroctonus  adjunctus  Blandford,  1897,  p.  147. 


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79980—09 12 


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Sta.  for  fiscal  year  ending  June  30,  1894. 
1897c.  HOPKINS,  A.  D. — Report  of  the  Entomological  Department. <9th  Ann.  Rep. 

W.  Va.  Agr.  Exp.  Sta.  for  fiscal  year  ending  June  30,  1896,  pp.  79, 94-95, 147, 

151,  PI.  I. 
1897.     BLANDFORD,  WALTER  F.  H. — Fam.  Scolytidae.<Biol.  Centr.-Amer.,  Coleopt., 

IV,  pt.  6,  August,  1897,  pp.  146,  147. 

1897.  CHITTENDEN,  F.  H. — Insect  injury  to  chestnut  and  pine  trees  in  Virginia  and 

neighboring  States.  Some  Miscellaneous  Results  of  the  Work  of  the  Division 
of  Entomology. <Bul.  7,  n.  s.,  Div.  Ent.,  U.  S.  Dept.  Agr.,  pp.  67-75,  fig.  43. 

1898.  HARVEY,  F.  L. — Notes  on  insects  of  the  year.<13th  Ann.  Rep.  Maine  Agr. 

Exp.  Sta.,  Orono,  Maine,  1897.  Part  II  of  the  Annual  Report  of  the  Uni- 
versity of  Maine,  p.  176.  Note  on  depredations  on  spruce  in  Maine. 

1898.  HOWARD,  L.  O.,  and  CHITTENDEN,  F.  H. — Notes  from  correspondence.  Some 
Miscellaneous  Results  of  the  Work  of  the  Division  of  Entomology. <Bul.  10, 
n.  s.,  Div.  Ent.,  U.  S.  Dept.  Agr.,  p.  98. 

1898a.  HOPKINS,  A.  D. — Proceedings  of  the  Tenth  Annual  Meeting  of  the  Association 
of  Economic  Entomologists. < Bui.  17,  n.  s.,  Div.  Ent.,  U.  S.  Dept.  Agr.,  p.  69. 

1898b.  HOPKINS,  A.  D. — Insects  detrimental  and  destructive  to  timber  and  timber 
products.  <  Proceedings  of  the  Nineteenth  Annual  Meeting  of  the  Society  for 
the  Promotion  of  Agricultural  Science,  held  at  Boston,  Mass.,  1898,  pp. 
104,  105. 

1898.     SCHWARZ,  E.  A.— Proc.  Ent.  Soc.  Wash.,  IV,  No.  2,  pp.  81,  82,  March  21. 

1898.  WEED,  CLARENCE  M.,  and  FISKE,  W.  F. — Notes  on  spruce  bark-beetles.  Pro- 
ceedings of  the  Tenth  Annual  Meeting  of  the  Association  of  Economic  Ento- 
mologists^ Bui.  17,  n.  s.,  Div.  Ent.,  U.  S.  Dept.  Agr.,  pp.  67-69. 

1898.  CHITTENDEN,  F.  II. — Recent  injury  by  bark-beetles.  A  correction.  Some 
Miscellaneous  Results  of  the  Work  of  the  Division  of  Entomology,  III.<Bul. 
18,  n.  s.,  Div.  Ent.,  IT.  S.  Dept.  Agr.,  p.  96. 

1898.  WICKHAM,  H.  F.— The  beetles  of  southern  Arizona,<Bul.  Lab.  Nat.  Hist, 
State  Univ.  Iowa,  Vol.  IV,  No.  3,  p.  312. 

1898.  JOHNSON,  CHAS.  W. — Report  on  insects  injurious  to  spruce  and  other  trees, 
Chap.  V.<3d  Ann.  Rep.  Pa.  Dept.  Agr.,  Part  II,  1897,  issued  in  1898  after 
September,  pp.  69-110. 

1898.  LOVENDAL,  E.  A. — De  Danske  barkbiller  (Scolytidae  et  Platypodidse  Danicae), 
pp.  86-91. 

1899a.  HOPKINS,  A.  D. — Report  on  investigations  to  determine  the  cause  of  unhealthy 
conditions  of  the  spruce  and  pine  from  1880-1893. <Bul.  56,  W.  Va.  Agr.  Exp. 
Sta.,  April. 


THE  (iExrs  I)|-:N  DINK  TOM'S.  1G3 

IMWIi.  HOPKINS,  A.  D.— Preliminary  report  on  the  insert  em-mics  of  forests  in  the 
northwest,  liul.  '21.  n.  a..  Div.  Knt.,  I".  S.  Dept.  Agr..  pp.  10.  II.  i:i  1  I. 
15,  20,  21.  -2-2.  2i>. 

I899c.  HOPKINS,  A.  D. — Notes  on  ])cnilr<H-tonnx.-  I'roc.  Km.  Soc.  Wash.,  1  V,  No.  :{, 
p.  343,  May  24. 

is!)!).  SMITH,  J.  B. — Insects  of  New  Jersey.  Supplement  to  the  27th  Annual  Report 
of  the  State  "Board  of  Agriculture,  p.  364. 

189!).  CHITTENDEN,  F.  H.— Insect  enemies  of  the  white  pine.  The  white  pine  (J'in  us 
strobus  Linnaeus).  Bui.  22,  Div.  For.,  U.  S.  Dept.  Agr.,  pp.  55,  56,  tigs.  5. 

1900a.  SCHWARZ,  E.  A. — Papers  from  the  Harriman  Alaska  Expedition,  XVIII. 
Entomological  results  (12);  Coleoptera.<Proc.  Wash.  Acad.  Sci.,  II,  p.  537, 
December  20. 

)b.  SCHWARZ,  E.  A. — Coleoptera  of  the  expedition. <Ibid.,  Author's  extra,  p.  185. 
CARY,  AUSTIN. — Insect  damage  to  spruce  timber,  in  Maine  and  New  Hamp- 
shire. <The  Forester,  VI,  No.  3,  pp.  52-54. 

1901.     SMITH,  J.  B.— Doings  of  societies. <Ent.  News,  XII,  No.  3,  p.  92,  March. 

1901.  JOHNSON. — Doings  of  societies. <Ent.  News,  XII,  No.  3,  p.  92,  March. 
1901a.  HOPKINS,  A.  D. — Insect  enemies  of  the  spruce  in  the  northeast. < Bui.  28,  n.  s., 

Div.  Ent.,  U.  S.  Dept.  Agr.,  pp.  1-48,  Pis.  I-V,  XIV,  XV  (issued  October  1, 
1901). 

1901b.  HOPKINS,  A.  D. — Some  insect  enemies  of  living  trees. <Proceedings  of  the 
Twenty-Second  Annual  Meeting  of  the  Society  for  the  Promotion  of  Agricul- 
tural Science  held  at  Denver,  Colo.,  pp.  66-69. 

1902.  SLOSSON,  A.  T. — Additional  list  of  insects  taken  in  the  Alpine  Region  of  Mount 

Washington. <Ent.  News,  pp.  319-321,  December,  1902. 
1902.     COMSTOCK,  J.  H.,  and  KELLOGG,  V.  L. — Elements  of  insect  anatomy.     Fourth 

edition . 
1902.     SEVERIN,  G. — Le  Dendroctonus  micans  (Kugelann)  en  Belgique.<Bull.  Soc. 

Centr.  forestiere  Belg.,  Vol.  IX,  pp.  72-81. 
1902.     SEVERIX,  G. — L'invasion  de  l'Hyl£sine  geante.<Bull.  Soc.  Centr.  forestiere 

Belg.,  Vol.  IX,  pp.  145-152. 
1902.     ULKE,  HENRY.— A  list  of  the  beetles  of  the  District  of  Columbia, <Proc.  U.  S. 

Nat.  Mus.,  XXV,  pp.  1-57. 
1902a.  HOPKINS,  A.  D. — Some  notes  on  the  genus  Dendroctonus. <Proc.  Ent.  Soc. 

Wash.,  V,  No.  1,  pp.  3-4,  May  17,  1902  (author's  extra  published  March  28, 

1902). 
19021>.  HOPKINS,  A.  D.— Insect  enemies  of  the  pine  in  the  Black  Hills  Forest  Reserve. 

<Bul.  32,  n.  s.,  Div.  Ent.,  U.  S.  Dept.  Agr.,  pp.  1-24,  Pis.  I-VII,  figs.  1-5 

(issued  April  29,  1902). 
UJILV.  HOPKINS,  A.  D. — On  the  study  of  forest  entomology  in  America.     Proceedings 

of  the  Fourteenth  Annual  Meeting  of  the  Association  of  Economic  Entomolo- 

gists.<Bul.  37,  n.  s.,  Div.  Ent.,  U.  S.  Dept.  Agr.,  pp.  5-32. 
1902.     SCHWARZ,  E.  A.— Proc.  Ent.  Soc.  Wash..  V,  No.  1,  p.  32,  May  17. 
1902.     WEBER,  L. — Zur  Biologic  von  Rhizophagus  grandis  Gyllh.<Allg.  Zeitsch.  f. 

Ent.,  VII,  p.  108. 

1902.  WICKHAM,  H.  F.— A  catalogue  of  the  Coleoptera  of  Colorado. <Bul.  Lab.  Nat. 

Hist.  State  Univ.  Iowa,  Vol.  V,  No.  3,  pp.  217-310. 
1903a.  HOPKINS,  A.  D. — Forest  insect  explorations  in  the  summer  of  1902. <( 'an. 

Ent.,  XXXV,  No.  3,  pp.  59-61,  March. 
1903b.  HOPKINS,  A.  D. — Some  of  the  principal  insect  enemies  of  coniferous  forests  in 

the  United  States. < Yearbook  U.  S.  Dept.  Agr.,  for  1902,  pp.  265-282. 

1903.  FELT,  E.  P.— Insects  affecting  forest  trees. <7th  Rep.  Forest,  Fish  and  Game 

Comm.  State  N.  Y.,  pp.  480-481,  2  plates,  figs.  1-3. 


164  THE  SCOLYTID  BEETLES. 

1903.  BRICHET,  0.,  et  SEVERIN,  G. — Le  Dendroctonus  micans,  de*gats  moyens  pre- 
ventifs  et  destructifs.<^Bull.  Soc.  Centr.  Forestiere  Belg..,  X,  pp.  244-258. 

1903.  BAUDISCH,  FR. — Uber  Dendroctonus  micans  Kug.<Centralbl.  ges.  Forstwesen^ 

Jahrg.  29,  pp.  151-152. 

1904.  HOPKINS,  A.  D. — Catalogue  of  exhibit  of  insect  enemies  of  forests  and  forest 

products  at  the  Louisiana  Purchase  Exposition,  St.  Louis,  Mo.,  1904. <   Bui. 
48,  Div.  Ent,,  U.  S.  Dept.  Agr. 

1904-5.  QUAIRIERE,  C. — Le  Dendroctonus  micans.^ Bull.  Soc.  Centr.  Forest  iere 
Belg.,  XI,  pp.  626-628;  XII,  pp.  183-186. 

1904.  POWELL,    P.   B. — The  development  of  wings  of  certain  beetles,   and  some 

studies  of  the  origin  of  the  wings  of  insects. <Journ.  N.  Y.  Ent.  Soc.,  XII, 
pp.  237-243,  Pis.  XI-XVII. 

1905.  Ibid,  (continued),  XIII,  pp.  5-22. 

1905.  HOPKINS,  A.  D. — The  Black  Hills  beetle,  with  further  notes  on  its  distribu- 
tion, life  history,  and  methods  of  control.  Bui.  56,  Bur.  Ent.,  U.  S.  Dept. 
Agr.,  pp.  1-24,  Pis.  I,  II,  figs.  1-6. 

1905.  QUIEVY,  PROSPER.—  Dendroctonus  micans,  invasion.  Bui.  Soc.  Centr.  Fores- 
tiere Belg.,  T.  12,  pp.  334-335. 

1905.  FELT,  E.  P. — Insects  affecting  park  and  woodland  trees.  X.  Y.  State  Mus., 
Mem.  8,  Vol.  1,  pp.  6r7. 

1905.     NUSSLIN,  O. — Leitfaden  der  Forstinsektenkunde,  pp.  175-178. 

1905.  Voss,  FRIEDRICH. — Uber  den  Thorax  von  Gryllus  domesticus,  mit  besonderer 

Beriicksichtigung  des  Fliigelgelenks  und  dessen   Bewegung.  -  Zeitschr.   f. 

wiss.  Zool.,  LXXVIII,  pp.  268-521,  654-759,  Pis.  XV,  XVI,  XXIV. 
1906a.  HOPKINS,  A.  D. — Barkbeetle  depredations  of  some  fifty  years  ago  in  the  Pikes 

Peak  region  of  Colorado.  <Proc.  Ent.  Soc.  Wash.,  VIII,  Nos.  1-2,  pp.  4-5,  July 

13,  1906. 
]Qo^    HOPKINS,  A.  D. — Notes  on  scolytid  larvae  and  their  mouthparts.     Proc.  Knt. 

Soc.  Wash.,  VII,  Nos.  2-3,  pp.  143-149,  Pis.  IV,  V,  January  10. 
1906c.  HOPKINS,  A.  D. — Notes  on  some  Mexican  Scolytidae,  with  descriptions  of  some 

new  species. <Proc.  Ent.  Soc.  Wash.,  VII,  Nos.  2-3,  pp.  71-81,  January  10. 

1906.  WEBB,  J.  L. — Some  insects  injurious  to  forests.     The  western  pine-destroying 

barkbeetle.<Bul.  58,  Pt.  II,  Bur.  Ent,,  U.  S.  Dept.  Agr.,  pp.  17-30,  Pis.  II, 
III,  figs.  7-12,  August  18. 

1906.  FELT,  E.  P. — Insects  affecting  park  and  woodland  trees.-    X.  Y.  State  \ 

Mem.  8,  Vol.  2. 

1907.  FALL,  H.  C.,  and  COCKERELL,  T.  D.  A.— The  Coleoptera  of  New  Me: 

<Trans.  Amer.  Ent,  Soc.,  XXXIII,  pp.  145,  218. 

1908.  SEVERIN,  G. — Le  genre  Dendroctonus. <Bull.    Soc.    Centr.   Foresti<Ve    Px 

Author's  extra,  pp.  1-20.     Received  May,  1908. 

1908.  HOPKINS,  A.  D. — Notable  depredations  by  forest  insects. <Yearbook  (  .  S 
Dept.  Agr.,  for  1907,  pp.  149-164. 


Tech.  Series  17,  Part  I,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


PLATE 


DENDROCTONUS  ADULTS. 

Fig.  1.— D.  brevicomis.    Fig.2.—D.barberi.    Fig.  3.— I),  conrcxifrons.    Fig.  4.— D.  frontalis.    Fig.  5, 
D.  arizonicus.    Fig.  6.— D.  mcxicanus.    Fig.  7.— D.  pamttclocollis.    (Original.) 


:h.  Series  17,  Part  I,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agricultur 


PLATE  IV. 


DENDROCTONUS  ADULTS. 

.  Yig.S.—D.monticola'.  Fig.  10.— />.  pmxlt  msr.  Fig.  11.— J>. 
(Original.) 


Tech.  Series  17,  Part  I,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


PLATE  VI. 


DENDROCTONUS  ADULTS. 

Fig.  17.— D.  obcsus.    Fig.  IN.— 7>. /•////>•/»//«.    Fig.  20.— D.  punctatus.    Fix.  •ll.—D.micans. 

(Original.) 


Tech.  Series  17,  Part  I,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


PLATE  VII. 


DENDROCTONUS  ADULTS. 

Fig.  22.— D.  terebrans.    Fig.  23.— D.  valens.    (Original.) 


Tech.  Series  17,  Part  I,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


PLATE  VIII. 


'232 


DENDROCTONUS  LARVXE. 

Fig.  1.— D.  brevicomte;  la,  spiracle,  enlarged;  Ib,  spiracle,  greatly  enlarged,  showing  simple 
bifid  processes.  Fig.  10.— D.  ponderosx,  spiracle,  greatly  enlarged.  Fig.  13.— D.  pseu- 
<tot.<ng£e,  spiracle,  greatly  enlarged.  Fig.  14.— D.  piceaperda,  spiracle,  greatly  enlarged. 
Fig.  19.— D.  murrayanx;.  19a,  dorsal  aspect  of  abdominal  segments  8  and  9,  showing 
plates;  19b,  anal  aspect:  19c,  19<7.  and  19e,  different  aspects  of  spiracular  tubercle,  much 
enlarged  Fig.  23.— D.  rnkns;  23a,  dorsal  aspect  of  thoracic  segments;  236,  dorsal  aspect 
of  abdominal  segments;  23c,  dorsal  aspect  of  abdominal  segments  8  and  9,  showing 
armed  plates;  23c/,  ventral  aspect  of  thoracic  segments;  23e,  ventral  aspect  of  abdominal 
segment:  23/,  anal  aspect  of  abdominal  segments  8,  9,  and  10;  23g,  23/i,  23*,  different 
aspects  of  spiracular  tubercles,  moderately  enlarged;  2Sj,  spiracle  and  spiracular  tubercle, 
greatly  enlarged.  (Original.) 


Tech.  Series  17,  Part  I,  Bureau  of  Entomology,  U.  S.  Dept.  of  Agriculture. 


PLATE  V. 


Fig.  IL>.—  J>.  simplex. 


DENDROCTONUS  ADULTS. 

.  p»  m/nt*^,;,:    Fig.  14.—  D.  piceaper<i>i.    Fig.  !<>.—  D.  Itorealis. 
(Original.) 


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